diff --git a/api/objects.pb.go b/api/objects.pb.go
index 74da298185..aea6330ff3 100644
--- a/api/objects.pb.go
+++ b/api/objects.pb.go
@@ -77,9 +77,18 @@ type Service struct {
 	ID   string      `protobuf:"bytes,1,opt,name=id,proto3" json:"id,omitempty"`
 	Meta Meta        `protobuf:"bytes,2,opt,name=meta" json:"meta"`
 	Spec ServiceSpec `protobuf:"bytes,3,opt,name=spec" json:"spec"`
+	// SpecVersion versions Spec, to identify changes in the spec. This is
+	// not a Version because it uses a different versioning scheme from
+	// top-level objects and is not directly comparable to top-level object
+	// versions.
+	SpecVersion uint64 `protobuf:"varint,10,opt,name=spec_version,json=specVersion,proto3" json:"spec_version,omitempty"`
 	// PreviousSpec is the previous service spec that was in place before
 	// "Spec".
 	PreviousSpec *ServiceSpec `protobuf:"bytes,6,opt,name=previous_spec,json=previousSpec" json:"previous_spec,omitempty"`
+	// PreviousSpecVersion versions PreviousSpec. This is not a Version
+	// because it uses a different versioning scheme from top-level
+	// objects and is not directly comparable to top-level object versions.
+	PreviousSpecVersion uint64 `protobuf:"varint,11,opt,name=previous_spec_version,json=previousSpecVersion,proto3" json:"previous_spec_version,omitempty"`
 	// Runtime state of service endpoint. This may be different
 	// from the spec version because the user may not have entered
 	// the optional fields like node_port or virtual_ip and it
@@ -140,6 +149,9 @@ type Task struct {
 	// Spec defines the desired state of the task as specified by the user.
 	// The system will honor this and will *never* modify it.
 	Spec TaskSpec `protobuf:"bytes,3,opt,name=spec" json:"spec"`
+	// SpecVersion is copied from Service, to identify which version of the
+	// spec this task has.
+	SpecVersion uint64 `protobuf:"varint,14,opt,name=spec_version,json=specVersion,proto3" json:"spec_version,omitempty"`
 	// ServiceID indicates the service under which this task is orchestrated. This
 	// should almost always be set.
 	ServiceID string `protobuf:"bytes,4,opt,name=service_id,json=serviceId,proto3" json:"service_id,omitempty"`
@@ -772,6 +784,16 @@ func (m *Service) MarshalTo(dAtA []byte) (int, error) {
 		}
 		i += n15
 	}
+	if m.SpecVersion != 0 {
+		dAtA[i] = 0x50
+		i++
+		i = encodeVarintObjects(dAtA, i, uint64(m.SpecVersion))
+	}
+	if m.PreviousSpecVersion != 0 {
+		dAtA[i] = 0x58
+		i++
+		i = encodeVarintObjects(dAtA, i, uint64(m.PreviousSpecVersion))
+	}
 	return i, nil
 }
 
@@ -972,6 +994,11 @@ func (m *Task) MarshalTo(dAtA []byte) (int, error) {
 		}
 		i += n23
 	}
+	if m.SpecVersion != 0 {
+		dAtA[i] = 0x70
+		i++
+		i = encodeVarintObjects(dAtA, i, uint64(m.SpecVersion))
+	}
 	return i, nil
 }
 
@@ -1348,6 +1375,12 @@ func (m *Service) Size() (n int) {
 		l = m.PreviousSpec.Size()
 		n += 1 + l + sovObjects(uint64(l))
 	}
+	if m.SpecVersion != 0 {
+		n += 1 + sovObjects(uint64(m.SpecVersion))
+	}
+	if m.PreviousSpecVersion != 0 {
+		n += 1 + sovObjects(uint64(m.PreviousSpecVersion))
+	}
 	return n
 }
 
@@ -1432,6 +1465,9 @@ func (m *Task) Size() (n int) {
 		l = m.LogDriver.Size()
 		n += 1 + l + sovObjects(uint64(l))
 	}
+	if m.SpecVersion != 0 {
+		n += 1 + sovObjects(uint64(m.SpecVersion))
+	}
 	return n
 }
 
@@ -1594,6 +1630,8 @@ func (this *Service) String() string {
 		`Endpoint:` + strings.Replace(fmt.Sprintf("%v", this.Endpoint), "Endpoint", "Endpoint", 1) + `,`,
 		`UpdateStatus:` + strings.Replace(fmt.Sprintf("%v", this.UpdateStatus), "UpdateStatus", "UpdateStatus", 1) + `,`,
 		`PreviousSpec:` + strings.Replace(fmt.Sprintf("%v", this.PreviousSpec), "ServiceSpec", "ServiceSpec", 1) + `,`,
+		`SpecVersion:` + fmt.Sprintf("%v", this.SpecVersion) + `,`,
+		`PreviousSpecVersion:` + fmt.Sprintf("%v", this.PreviousSpecVersion) + `,`,
 		`}`,
 	}, "")
 	return s
@@ -1639,6 +1677,7 @@ func (this *Task) String() string {
 		`Networks:` + strings.Replace(fmt.Sprintf("%v", this.Networks), "NetworkAttachment", "NetworkAttachment", 1) + `,`,
 		`Endpoint:` + strings.Replace(fmt.Sprintf("%v", this.Endpoint), "Endpoint", "Endpoint", 1) + `,`,
 		`LogDriver:` + strings.Replace(fmt.Sprintf("%v", this.LogDriver), "Driver", "Driver", 1) + `,`,
+		`SpecVersion:` + fmt.Sprintf("%v", this.SpecVersion) + `,`,
 		`}`,
 	}, "")
 	return s
@@ -2397,6 +2436,44 @@ func (m *Service) Unmarshal(dAtA []byte) error {
 				return err
 			}
 			iNdEx = postIndex
+		case 10:
+			if wireType != 0 {
+				return fmt.Errorf("proto: wrong wireType = %d for field SpecVersion", wireType)
+			}
+			m.SpecVersion = 0
+			for shift := uint(0); ; shift += 7 {
+				if shift >= 64 {
+					return ErrIntOverflowObjects
+				}
+				if iNdEx >= l {
+					return io.ErrUnexpectedEOF
+				}
+				b := dAtA[iNdEx]
+				iNdEx++
+				m.SpecVersion |= (uint64(b) & 0x7F) << shift
+				if b < 0x80 {
+					break
+				}
+			}
+		case 11:
+			if wireType != 0 {
+				return fmt.Errorf("proto: wrong wireType = %d for field PreviousSpecVersion", wireType)
+			}
+			m.PreviousSpecVersion = 0
+			for shift := uint(0); ; shift += 7 {
+				if shift >= 64 {
+					return ErrIntOverflowObjects
+				}
+				if iNdEx >= l {
+					return io.ErrUnexpectedEOF
+				}
+				b := dAtA[iNdEx]
+				iNdEx++
+				m.PreviousSpecVersion |= (uint64(b) & 0x7F) << shift
+				if b < 0x80 {
+					break
+				}
+			}
 		default:
 			iNdEx = preIndex
 			skippy, err := skipObjects(dAtA[iNdEx:])
@@ -3072,6 +3149,25 @@ func (m *Task) Unmarshal(dAtA []byte) error {
 				return err
 			}
 			iNdEx = postIndex
+		case 14:
+			if wireType != 0 {
+				return fmt.Errorf("proto: wrong wireType = %d for field SpecVersion", wireType)
+			}
+			m.SpecVersion = 0
+			for shift := uint(0); ; shift += 7 {
+				if shift >= 64 {
+					return ErrIntOverflowObjects
+				}
+				if iNdEx >= l {
+					return io.ErrUnexpectedEOF
+				}
+				b := dAtA[iNdEx]
+				iNdEx++
+				m.SpecVersion |= (uint64(b) & 0x7F) << shift
+				if b < 0x80 {
+					break
+				}
+			}
 		default:
 			iNdEx = preIndex
 			skippy, err := skipObjects(dAtA[iNdEx:])
@@ -4077,79 +4173,82 @@ var (
 func init() { proto.RegisterFile("objects.proto", fileDescriptorObjects) }
 
 var fileDescriptorObjects = []byte{
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+	// 1222 bytes of a gzipped FileDescriptorProto
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+	0x05, 0x34, 0x7f, 0xd6, 0xd9, 0xc8, 0xeb, 0xb4, 0x95, 0xaa, 0xdc, 0x66, 0x3c, 0xdf, 0xf7, 0xfb,
+	0x97, 0x6f, 0xbe, 0x9d, 0x40, 0x93, 0x1d, 0xfd, 0x48, 0x03, 0x29, 0xba, 0x29, 0x67, 0x92, 0x21,
+	0x14, 0xb2, 0x60, 0x4c, 0x79, 0x57, 0x3c, 0x21, 0x7c, 0x32, 0x8e, 0x64, 0x77, 0xf6, 0xe1, 0x76,
+	0x43, 0xce, 0x53, 0x6a, 0x01, 0xdb, 0x0d, 0x91, 0xd2, 0x20, 0xdb, 0xb4, 0x47, 0x8c, 0x8d, 0x62,
+	0x7a, 0x43, 0xef, 0x8e, 0xa6, 0x8f, 0x6f, 0xc8, 0x68, 0x42, 0x85, 0x24, 0x93, 0xd4, 0x02, 0x2e,
+	0x8d, 0xd8, 0x88, 0xe9, 0xe5, 0x0d, 0xb5, 0x32, 0xbf, 0x76, 0xfe, 0x72, 0xc0, 0xbd, 0x4b, 0x25,
+	0x41, 0x9f, 0x41, 0x75, 0x46, 0xb9, 0x88, 0x58, 0xe2, 0x39, 0xbb, 0xce, 0xb5, 0xc6, 0xde, 0xdb,
+	0xdd, 0xd5, 0xfc, 0xdd, 0x87, 0x06, 0xd2, 0x77, 0x9f, 0x1e, 0xb7, 0x2f, 0xe0, 0x8c, 0x81, 0x6e,
+	0x01, 0x04, 0x9c, 0x12, 0x49, 0x43, 0x9f, 0x48, 0xaf, 0xa4, 0xf9, 0xdb, 0x5d, 0x53, 0x51, 0x37,
+	0xab, 0xa8, 0xfb, 0x20, 0xab, 0x08, 0xd7, 0x2d, 0xba, 0x27, 0x15, 0x75, 0x9a, 0x86, 0x19, 0xb5,
+	0xfc, 0x7c, 0xaa, 0x45, 0xf7, 0x64, 0xe7, 0x57, 0x17, 0xdc, 0x6f, 0x59, 0x48, 0xd1, 0x65, 0x28,
+	0x45, 0xa1, 0x2e, 0xbb, 0xde, 0xaf, 0x2c, 0x8e, 0xdb, 0xa5, 0xe1, 0x01, 0x2e, 0x45, 0x21, 0xda,
+	0x03, 0x77, 0x42, 0x25, 0xb1, 0x05, 0x79, 0x45, 0x0d, 0xa9, 0xde, 0x6d, 0x37, 0x1a, 0x8b, 0x3e,
+	0x01, 0x57, 0x8d, 0xd5, 0x56, 0xb2, 0x53, 0xc4, 0x51, 0x39, 0xef, 0xa7, 0x34, 0xc8, 0x78, 0x0a,
+	0x8f, 0x0e, 0xa1, 0x11, 0x52, 0x11, 0xf0, 0x28, 0x95, 0x6a, 0x86, 0xae, 0xa6, 0x5f, 0x5d, 0x47,
+	0x3f, 0x38, 0x81, 0xe2, 0x3c, 0x0f, 0x7d, 0x0e, 0x15, 0x21, 0x89, 0x9c, 0x0a, 0x6f, 0x43, 0x47,
+	0x68, 0xad, 0x2d, 0x40, 0xa3, 0x6c, 0x09, 0x96, 0x83, 0xbe, 0x86, 0xad, 0x09, 0x49, 0xc8, 0x88,
+	0x72, 0xdf, 0x46, 0xa9, 0xe8, 0x28, 0x57, 0x0a, 0x5b, 0x37, 0x48, 0x13, 0x08, 0x37, 0x27, 0xf9,
+	0x2d, 0x3a, 0x04, 0x20, 0x52, 0x92, 0xe0, 0x87, 0x09, 0x4d, 0xa4, 0x57, 0xd5, 0x51, 0xde, 0x2d,
+	0xac, 0x85, 0xca, 0x27, 0x8c, 0x8f, 0x7b, 0x4b, 0x30, 0xce, 0x11, 0xd1, 0x57, 0xd0, 0x08, 0x28,
+	0x97, 0xd1, 0xe3, 0x28, 0x20, 0x92, 0x7a, 0x35, 0x1d, 0xa7, 0x5d, 0x14, 0x67, 0x70, 0x02, 0xb3,
+	0x4d, 0xe5, 0x99, 0xe8, 0x03, 0x70, 0x39, 0x8b, 0xa9, 0x57, 0xdf, 0x75, 0xae, 0x6d, 0xad, 0xff,
+	0xb3, 0x60, 0x16, 0x53, 0xac, 0x91, 0x9d, 0x3f, 0xcb, 0x50, 0xbd, 0x4f, 0xf9, 0x2c, 0x0a, 0x5e,
+	0xad, 0x40, 0x6e, 0x9d, 0x12, 0x48, 0x61, 0x2f, 0x36, 0xed, 0x8a, 0x46, 0xf6, 0xa1, 0x46, 0x93,
+	0x30, 0x65, 0x51, 0x22, 0xad, 0x40, 0x0a, 0x1b, 0x39, 0xb4, 0x18, 0xbc, 0x44, 0xa3, 0x43, 0x68,
+	0x1a, 0xdd, 0xfb, 0xa7, 0xd4, 0xb1, 0x5b, 0x44, 0xff, 0x5e, 0x03, 0xed, 0x9f, 0x75, 0x73, 0x9a,
+	0xdb, 0xa1, 0x03, 0x68, 0xa6, 0x9c, 0xce, 0x22, 0x36, 0x15, 0xbe, 0x6e, 0xa2, 0xf2, 0x42, 0x4d,
+	0xe0, 0xcd, 0x8c, 0xa5, 0x76, 0xe8, 0x0a, 0x6c, 0x2a, 0xb2, 0x9f, 0xf9, 0x05, 0xec, 0x3a, 0xd7,
+	0x5c, 0xac, 0xdd, 0xc8, 0xfa, 0x03, 0xda, 0x83, 0x37, 0x4e, 0x25, 0x5a, 0x62, 0x1b, 0x1a, 0x7b,
+	0x31, 0x1f, 0xcf, 0x72, 0x3a, 0xbf, 0x95, 0xa0, 0x96, 0xb5, 0x8e, 0x6e, 0xda, 0x29, 0x3b, 0xeb,
+	0xfb, 0xcc, 0xb0, 0xba, 0x42, 0x33, 0xe0, 0x9b, 0xb0, 0x91, 0x32, 0x2e, 0x85, 0x57, 0xda, 0x2d,
+	0xaf, 0xbb, 0x3c, 0xf7, 0x18, 0x97, 0x03, 0x96, 0x3c, 0x8e, 0x46, 0xd8, 0x80, 0xd1, 0x23, 0x68,
+	0xcc, 0x22, 0x2e, 0xa7, 0x24, 0xf6, 0xa3, 0x54, 0x78, 0x65, 0xcd, 0x7d, 0xef, 0xac, 0x94, 0xdd,
+	0x87, 0x06, 0x3f, 0xbc, 0xd7, 0xdf, 0x5a, 0x1c, 0xb7, 0x61, 0xb9, 0x15, 0x18, 0x6c, 0xa8, 0x61,
+	0x2a, 0xb6, 0xef, 0x42, 0x7d, 0x79, 0x82, 0xae, 0x03, 0x24, 0xe6, 0xae, 0xf8, 0x4b, 0x2d, 0x36,
+	0x17, 0xc7, 0xed, 0xba, 0xbd, 0x41, 0xc3, 0x03, 0x5c, 0xb7, 0x80, 0x61, 0x88, 0x10, 0xb8, 0x24,
+	0x0c, 0xb9, 0x56, 0x66, 0x1d, 0xeb, 0x75, 0xe7, 0xbf, 0x0d, 0x70, 0x1f, 0x10, 0x31, 0x3e, 0x6f,
+	0xbf, 0x53, 0x39, 0x57, 0xb4, 0x7c, 0x1d, 0x40, 0x18, 0x85, 0xa8, 0x76, 0xdc, 0x93, 0x76, 0xac,
+	0x6e, 0x54, 0x3b, 0x16, 0x60, 0xda, 0x11, 0x31, 0x93, 0x5a, 0xb6, 0x2e, 0xd6, 0x6b, 0x74, 0x15,
+	0xaa, 0x09, 0x0b, 0x35, 0xbd, 0xa2, 0xe9, 0xb0, 0x38, 0x6e, 0x57, 0xd4, 0x2d, 0x1e, 0x1e, 0xe0,
+	0x8a, 0x3a, 0x1a, 0x86, 0xca, 0x40, 0x48, 0x92, 0x30, 0x49, 0x94, 0x3b, 0x0a, 0x6b, 0x44, 0x85,
+	0x7a, 0xed, 0x9d, 0xc0, 0x32, 0x03, 0xc9, 0x31, 0xd1, 0x43, 0xb8, 0x98, 0xd5, 0x9b, 0x0f, 0x58,
+	0x7b, 0x99, 0x80, 0xc8, 0x46, 0xc8, 0x9d, 0xe4, 0x0c, 0xbb, 0xbe, 0xde, 0xb0, 0xf5, 0x04, 0x8b,
+	0x0c, 0xbb, 0x0f, 0xcd, 0x90, 0x8a, 0x88, 0xd3, 0x50, 0x5f, 0x6c, 0xaa, 0xef, 0xd2, 0xd6, 0xde,
+	0x3b, 0x67, 0x05, 0xa1, 0x78, 0xd3, 0x72, 0xf4, 0x0e, 0xf5, 0xa0, 0x66, 0x75, 0x23, 0xbc, 0x86,
+	0xd6, 0xee, 0x0b, 0x1a, 0xf5, 0x92, 0x76, 0xca, 0x98, 0x36, 0x5f, 0xca, 0x98, 0x6e, 0x01, 0xc4,
+	0x6c, 0xe4, 0x87, 0x3c, 0x9a, 0x51, 0xee, 0x35, 0xed, 0xe7, 0xbb, 0x80, 0x7b, 0xa0, 0x11, 0xb8,
+	0x1e, 0xb3, 0x91, 0x59, 0xae, 0xd8, 0xc8, 0xd6, 0x8a, 0x8d, 0x74, 0x7e, 0x76, 0xe0, 0xf5, 0x95,
+	0xba, 0xd1, 0xc7, 0x50, 0xb5, 0x95, 0x9f, 0xf5, 0x54, 0xb1, 0x3c, 0x9c, 0x61, 0xd1, 0x0e, 0xd4,
+	0xd5, 0x35, 0xa2, 0x42, 0x50, 0x63, 0x10, 0x75, 0x7c, 0xf2, 0x03, 0xf2, 0xa0, 0x4a, 0xe2, 0x88,
+	0xa8, 0xb3, 0xb2, 0x3e, 0xcb, 0xb6, 0x9d, 0x5f, 0x4a, 0x50, 0xb5, 0xc1, 0xce, 0xfb, 0x43, 0x62,
+	0xd3, 0xae, 0x5c, 0xbe, 0xdb, 0xb0, 0x69, 0x26, 0x6e, 0x55, 0xe3, 0x3e, 0x77, 0xee, 0x0d, 0x83,
+	0x37, 0x8a, 0xb9, 0x0d, 0x6e, 0x94, 0x92, 0x89, 0xfd, 0x88, 0x14, 0x66, 0x1e, 0xde, 0xeb, 0xdd,
+	0xfd, 0x2e, 0x35, 0xe2, 0xaf, 0x2d, 0x8e, 0xdb, 0xae, 0xfa, 0x01, 0x6b, 0x5a, 0xe7, 0xf7, 0x0d,
+	0xa8, 0x0e, 0xe2, 0xa9, 0x90, 0x94, 0x9f, 0xf7, 0x40, 0x6c, 0xda, 0x95, 0x81, 0x0c, 0xa0, 0xca,
+	0x19, 0x93, 0x7e, 0x40, 0xce, 0x9a, 0x05, 0x66, 0x4c, 0x0e, 0x7a, 0xfd, 0x2d, 0x45, 0x54, 0x5e,
+	0x63, 0xf6, 0xb8, 0xa2, 0xa8, 0x03, 0x82, 0x1e, 0xc1, 0xe5, 0xcc, 0xa1, 0x8f, 0x18, 0x93, 0x42,
+	0x72, 0x92, 0xfa, 0x63, 0x3a, 0x57, 0x5f, 0xdb, 0xf2, 0xba, 0x57, 0xd4, 0x61, 0x12, 0xf0, 0xb9,
+	0x1e, 0xd4, 0x1d, 0x3a, 0xc7, 0x97, 0x6c, 0x80, 0x7e, 0xc6, 0xbf, 0x43, 0xe7, 0x02, 0x7d, 0x01,
+	0x3b, 0x74, 0x09, 0x53, 0x11, 0xfd, 0x98, 0x4c, 0xd4, 0xb7, 0xc7, 0x0f, 0x62, 0x16, 0x8c, 0xb5,
+	0xfd, 0xb9, 0xf8, 0x2d, 0x9a, 0x0f, 0xf5, 0x8d, 0x41, 0x0c, 0x14, 0x00, 0x09, 0xf0, 0x8e, 0x62,
+	0x12, 0x8c, 0xe3, 0x48, 0xa8, 0x87, 0x72, 0xee, 0x61, 0xa4, 0x1c, 0x4c, 0xd5, 0xb6, 0x7f, 0xc6,
+	0xb4, 0xba, 0xfd, 0x13, 0x6e, 0xee, 0x99, 0x25, 0x0e, 0x13, 0xc9, 0xe7, 0xf8, 0xcd, 0xa3, 0xe2,
+	0x53, 0xd4, 0x87, 0xc6, 0x34, 0x51, 0xe9, 0xcd, 0x0c, 0xea, 0x2f, 0x3a, 0x03, 0x30, 0x2c, 0xd5,
+	0xf9, 0xf6, 0x0c, 0x76, 0xce, 0x4a, 0x8e, 0x5e, 0x83, 0xf2, 0x98, 0xce, 0x8d, 0x7e, 0xb0, 0x5a,
+	0xa2, 0x2f, 0x61, 0x63, 0x46, 0xe2, 0x29, 0xb5, 0xca, 0x79, 0xbf, 0x28, 0x5f, 0x71, 0x48, 0x6c,
+	0x88, 0x9f, 0x96, 0xf6, 0x9d, 0xce, 0x1f, 0x0e, 0x54, 0xee, 0xd3, 0x80, 0x53, 0xf9, 0x4a, 0x15,
+	0xba, 0x7f, 0x4a, 0xa1, 0xad, 0xe2, 0x67, 0x93, 0xca, 0xba, 0x22, 0xd0, 0x6d, 0xa8, 0x45, 0x89,
+	0xa4, 0x3c, 0x21, 0xb1, 0x56, 0x68, 0x0d, 0x2f, 0xf7, 0x7d, 0xef, 0xe9, 0xb3, 0xd6, 0x85, 0x7f,
+	0x9e, 0xb5, 0x2e, 0xfc, 0xb4, 0x68, 0x39, 0x4f, 0x17, 0x2d, 0xe7, 0xef, 0x45, 0xcb, 0xf9, 0x77,
+	0xd1, 0x72, 0x8e, 0x2a, 0xfa, 0x1f, 0xa0, 0x8f, 0xfe, 0x0f, 0x00, 0x00, 0xff, 0xff, 0x56, 0x1e,
+	0x34, 0x83, 0x1a, 0x0e, 0x00, 0x00,
 }
diff --git a/api/objects.proto b/api/objects.proto
index 36b7a4addb..c86f6b0619 100644
--- a/api/objects.proto
+++ b/api/objects.proto
@@ -69,10 +69,21 @@ message Service {
 
 	ServiceSpec spec = 3 [(gogoproto.nullable) = false];
 
+	// SpecVersion versions Spec, to identify changes in the spec. This is
+	// not a Version because it uses a different versioning scheme from
+	// top-level objects and is not directly comparable to top-level object
+	// versions.
+	uint64 spec_version = 10;
+
 	// PreviousSpec is the previous service spec that was in place before
 	// "Spec".
 	ServiceSpec previous_spec = 6;
 
+	// PreviousSpecVersion versions PreviousSpec. This is not a Version
+	// because it uses a different versioning scheme from top-level
+	// objects and is not directly comparable to top-level object versions.
+	uint64 previous_spec_version = 11;
+
 	// Runtime state of service endpoint. This may be different
 	// from the spec version because the user may not have entered
 	// the optional fields like node_port or virtual_ip and it
@@ -131,6 +142,10 @@ message Task {
 	// The system will honor this and will *never* modify it.
 	TaskSpec spec = 3 [(gogoproto.nullable) = false];
 
+	// SpecVersion is copied from Service, to identify which version of the
+	// spec this task has.
+	uint64 spec_version = 14;
+
 	// ServiceID indicates the service under which this task is orchestrated. This
 	// should almost always be set.
 	string service_id = 4;
diff --git a/manager/controlapi/service.go b/manager/controlapi/service.go
index b5e8710a4b..f510e5f842 100644
--- a/manager/controlapi/service.go
+++ b/manager/controlapi/service.go
@@ -476,8 +476,9 @@ func (s *Server) CreateService(ctx context.Context, request *api.CreateServiceRe
 	// TODO(aluzzardi): Consider using `Name` as a primary key to handle
 	// duplicate creations. See #65
 	service := &api.Service{
-		ID:   identity.NewID(),
-		Spec: *request.Spec,
+		ID:          identity.NewID(),
+		Spec:        *request.Spec,
+		SpecVersion: 1,
 	}
 
 	if doesServiceNeedIngress(service) {
@@ -599,8 +600,11 @@ func (s *Server) UpdateService(ctx context.Context, request *api.UpdateServiceRe
 			}
 
 			curSpec := service.Spec.Copy()
+			curSpecVersion := service.SpecVersion
 			service.Spec = *service.PreviousSpec.Copy()
+			service.SpecVersion = service.PreviousSpecVersion
 			service.PreviousSpec = curSpec
+			service.PreviousSpecVersion = curSpecVersion
 
 			service.UpdateStatus = &api.UpdateStatus{
 				State:     api.UpdateStatus_ROLLBACK_STARTED,
@@ -609,7 +613,9 @@ func (s *Server) UpdateService(ctx context.Context, request *api.UpdateServiceRe
 			}
 		} else {
 			service.PreviousSpec = service.Spec.Copy()
+			service.PreviousSpecVersion = service.SpecVersion
 			service.Spec = *request.Spec.Copy()
+			service.SpecVersion++
 
 			// Reset update status
 			service.UpdateStatus = nil
diff --git a/manager/orchestrator/task.go b/manager/orchestrator/task.go
index 9197eee4c0..94cd898d26 100644
--- a/manager/orchestrator/task.go
+++ b/manager/orchestrator/task.go
@@ -29,6 +29,7 @@ func NewTask(cluster *api.Cluster, service *api.Service, slot uint64, nodeID str
 		ID:                 taskID,
 		ServiceAnnotations: service.Spec.Annotations,
 		Spec:               service.Spec.Task,
+		SpecVersion:        service.SpecVersion,
 		ServiceID:          service.ID,
 		Slot:               slot,
 		Status: api.TaskStatus{
@@ -62,6 +63,13 @@ func RestartCondition(task *api.Task) api.RestartPolicy_RestartCondition {
 
 // IsTaskDirty determines whether a task matches the given service's spec.
 func IsTaskDirty(s *api.Service, t *api.Task) bool {
+	// If the spec version matches, we know the task is not dirty. However,
+	// if it does not match, that doesn't mean the task is dirty, since
+	// only a portion of the spec is included in the comparison.
+	if t.SpecVersion != 0 && s.SpecVersion == t.SpecVersion {
+		return false
+	}
+
 	return !reflect.DeepEqual(s.Spec.Task, t.Spec) ||
 		(t.Endpoint != nil && !reflect.DeepEqual(s.Spec.Endpoint, t.Endpoint.Spec))
 }
diff --git a/manager/scheduler/scheduler.go b/manager/scheduler/scheduler.go
index 7935187e93..67d1b8f2e6 100644
--- a/manager/scheduler/scheduler.go
+++ b/manager/scheduler/scheduler.go
@@ -331,7 +331,12 @@ func (s *Scheduler) processPreassignedTasks(ctx context.Context) {
 
 // tick attempts to schedule the queue.
 func (s *Scheduler) tick(ctx context.Context) {
-	tasksByCommonSpec := make(map[string]map[string]*api.Task)
+	type commonSpecKey struct {
+		serviceID   string
+		specVersion uint64
+	}
+	tasksByCommonSpec := make(map[commonSpecKey]map[string]*api.Task)
+	var oneOffTasks []*api.Task
 	schedulingDecisions := make(map[string]schedulingDecision, len(s.unassignedTasks))
 
 	for taskID, t := range s.unassignedTasks {
@@ -341,30 +346,31 @@ func (s *Scheduler) tick(ctx context.Context) {
 			continue
 		}
 
-		// Group common tasks with common specs by marshalling the spec
-		// into taskKey and using it as a map key.
-		// TODO(aaronl): Once specs are versioned, this will allow a
-		// much more efficient fast path.
-		fieldsToMarshal := api.Task{
-			ServiceID: t.ServiceID,
-			Spec:      t.Spec,
-		}
-		marshalled, err := fieldsToMarshal.Marshal()
-		if err != nil {
-			panic(err)
-		}
-		taskGroupKey := string(marshalled)
+		// Group tasks with common specs
+		if t.SpecVersion != 0 {
+			taskGroupKey := commonSpecKey{
+				serviceID:   t.ServiceID,
+				specVersion: t.SpecVersion,
+			}
 
-		if tasksByCommonSpec[taskGroupKey] == nil {
-			tasksByCommonSpec[taskGroupKey] = make(map[string]*api.Task)
+			if tasksByCommonSpec[taskGroupKey] == nil {
+				tasksByCommonSpec[taskGroupKey] = make(map[string]*api.Task)
+			}
+			tasksByCommonSpec[taskGroupKey][taskID] = t
+		} else {
+			// This task doesn't have a spec version. We have to
+			// schedule it as a one-off.
+			oneOffTasks = append(oneOffTasks, t)
 		}
-		tasksByCommonSpec[taskGroupKey][taskID] = t
 		delete(s.unassignedTasks, taskID)
 	}
 
 	for _, taskGroup := range tasksByCommonSpec {
 		s.scheduleTaskGroup(ctx, taskGroup, schedulingDecisions)
 	}
+	for _, t := range oneOffTasks {
+		s.scheduleTaskGroup(ctx, map[string]*api.Task{t.ID: t}, schedulingDecisions)
+	}
 
 	_, failed := s.applySchedulingDecisions(ctx, schedulingDecisions)
 	for _, decision := range failed {
diff --git a/manager/scheduler/scheduler_test.go b/manager/scheduler/scheduler_test.go
index 0d28632cce..e7bd7cf914 100644
--- a/manager/scheduler/scheduler_test.go
+++ b/manager/scheduler/scheduler_test.go
@@ -367,7 +367,7 @@ func TestScheduler(t *testing.T) {
 	assert.NotEqual(t, "id6", assignment8.NodeID)
 }
 
-func TestHA(t *testing.T) {
+func testHA(t *testing.T, useSpecVersion bool) {
 	ctx := context.Background()
 	initialNodeSet := []*api.Node{
 		{
@@ -432,6 +432,11 @@ func TestHA(t *testing.T) {
 		},
 	}
 
+	if useSpecVersion {
+		taskTemplate1.SpecVersion = 1
+		taskTemplate2.SpecVersion = 1
+	}
+
 	s := store.NewMemoryStore(nil)
 	assert.NotNil(t, s)
 	defer s.Close()
@@ -641,7 +646,12 @@ func TestHA(t *testing.T) {
 	assert.Equal(t, 1, t2Assignments["id1"])
 }
 
-func TestPreferences(t *testing.T) {
+func TestHA(t *testing.T) {
+	t.Run("useSpecVersion=false", func(t *testing.T) { testHA(t, false) })
+	t.Run("useSpecVersion=true", func(t *testing.T) { testHA(t, true) })
+}
+
+func testPreferences(t *testing.T, useSpecVersion bool) {
 	ctx := context.Background()
 	initialNodeSet := []*api.Node{
 		{
@@ -737,6 +747,10 @@ func TestPreferences(t *testing.T) {
 		},
 	}
 
+	if useSpecVersion {
+		taskTemplate1.SpecVersion = 1
+	}
+
 	s := store.NewMemoryStore(nil)
 	assert.NotNil(t, s)
 	defer s.Close()
@@ -785,7 +799,12 @@ func TestPreferences(t *testing.T) {
 	assert.Equal(t, 1, t1Assignments["id5"])
 }
 
-func TestMultiplePreferences(t *testing.T) {
+func TestPreferences(t *testing.T) {
+	t.Run("useSpecVersion=false", func(t *testing.T) { testPreferences(t, false) })
+	t.Run("useSpecVersion=true", func(t *testing.T) { testPreferences(t, true) })
+}
+
+func testMultiplePreferences(t *testing.T, useSpecVersion bool) {
 	ctx := context.Background()
 	initialNodeSet := []*api.Node{
 		{
@@ -968,6 +987,10 @@ func TestMultiplePreferences(t *testing.T) {
 		},
 	}
 
+	if useSpecVersion {
+		taskTemplate1.SpecVersion = 1
+	}
+
 	s := store.NewMemoryStore(nil)
 	assert.NotNil(t, s)
 	defer s.Close()
@@ -1057,6 +1080,11 @@ func TestMultiplePreferences(t *testing.T) {
 	}
 }
 
+func TestMultiplePreferences(t *testing.T) {
+	t.Run("useSpecVersion=false", func(t *testing.T) { testMultiplePreferences(t, false) })
+	t.Run("useSpecVersion=true", func(t *testing.T) { testMultiplePreferences(t, true) })
+}
+
 func TestSchedulerNoReadyNodes(t *testing.T) {
 	ctx := context.Background()
 	initialTask := &api.Task{