diff --git a/cmd/dep/ensure.go b/cmd/dep/ensure.go
index 1a5cc465c2..07157b14b5 100644
--- a/cmd/dep/ensure.go
+++ b/cmd/dep/ensure.go
@@ -226,6 +226,13 @@ func (cmd *ensureCommand) validateFlags() error {
 	return nil
 }
 
+func (cmd *ensureCommand) vendorBehavior() dep.VendorBehavior {
+	if cmd.noVendor {
+		return dep.VendorNever
+	}
+	return dep.VendorOnChanged
+}
+
 func (cmd *ensureCommand) runDefault(ctx *dep.Ctx, args []string, p *dep.Project, sm gps.SourceManager, params gps.SolveParameters) error {
 	// Bare ensure doesn't take any args.
 	if len(args) != 0 {
@@ -283,11 +290,7 @@ func (cmd *ensureCommand) runDefault(ctx *dep.Ctx, args []string, p *dep.Project
 		return handleAllTheFailuresOfTheWorld(err)
 	}
 
-	vendorBehavior := dep.VendorOnChanged
-	if cmd.noVendor {
-		vendorBehavior = dep.VendorNever
-	}
-	sw, err := dep.NewSafeWriter(nil, p.Lock, dep.LockFromSolution(solution), vendorBehavior)
+	sw, err := dep.NewSafeWriter(nil, p.Lock, dep.LockFromSolution(solution), cmd.vendorBehavior())
 	if err != nil {
 		return err
 	}
@@ -377,7 +380,7 @@ func (cmd *ensureCommand) runUpdate(ctx *dep.Ctx, args []string, p *dep.Project,
 		return handleAllTheFailuresOfTheWorld(err)
 	}
 
-	sw, err := dep.NewSafeWriter(nil, p.Lock, dep.LockFromSolution(solution), dep.VendorOnChanged)
+	sw, err := dep.NewSafeWriter(nil, p.Lock, dep.LockFromSolution(solution), cmd.vendorBehavior())
 	if err != nil {
 		return err
 	}
diff --git a/cmd/dep/testdata/harness_tests/ensure/update/novendor/final/Gopkg.lock b/cmd/dep/testdata/harness_tests/ensure/update/novendor/final/Gopkg.lock
new file mode 100644
index 0000000000..c7f497e7a1
--- /dev/null
+++ b/cmd/dep/testdata/harness_tests/ensure/update/novendor/final/Gopkg.lock
@@ -0,0 +1,15 @@
+# This file is autogenerated, do not edit; changes may be undone by the next 'dep ensure'.
+
+
+[[projects]]
+  name = "github.com/sdboyer/deptest"
+  packages = ["."]
+  revision = "ff2948a2ac8f538c4ecd55962e919d1e13e74baf"
+  version = "v1.0.0"
+
+[solve-meta]
+  analyzer-name = "dep"
+  analyzer-version = 1
+  inputs-digest = "14b07b05e0f01051b03887ab2bf80b516bc5510ea92f75f76c894b1745d8850c"
+  solver-name = "gps-cdcl"
+  solver-version = 1
diff --git a/cmd/dep/testdata/harness_tests/ensure/update/novendor/final/Gopkg.toml b/cmd/dep/testdata/harness_tests/ensure/update/novendor/final/Gopkg.toml
new file mode 100644
index 0000000000..e242e02114
--- /dev/null
+++ b/cmd/dep/testdata/harness_tests/ensure/update/novendor/final/Gopkg.toml
@@ -0,0 +1,4 @@
+
+[[constraint]]
+  name = "github.com/sdboyer/deptest"
+  version = "1.0.0"
diff --git a/cmd/dep/testdata/harness_tests/ensure/update/novendor/initial/Gopkg.lock b/cmd/dep/testdata/harness_tests/ensure/update/novendor/initial/Gopkg.lock
new file mode 100644
index 0000000000..8ffcb4775b
--- /dev/null
+++ b/cmd/dep/testdata/harness_tests/ensure/update/novendor/initial/Gopkg.lock
@@ -0,0 +1,15 @@
+# This file is autogenerated, do not edit; changes may be undone by the next 'dep ensure'.
+
+
+[[projects]]
+  name = "github.com/sdboyer/deptest"
+  packages = ["."]
+  revision = "ff2948a2ac8f538c4ecd55962e919d1e13e74baf"
+  version = "v0.8.0"
+
+[solve-meta]
+  analyzer-name = "dep"
+  analyzer-version = 1
+  inputs-digest = "14b07b05e0f01051b03887ab2bf80b516bc5510ea92f75f76c894b1745d8850c"
+  solver-name = "gps-cdcl"
+  solver-version = 1
diff --git a/cmd/dep/testdata/harness_tests/ensure/update/novendor/initial/Gopkg.toml b/cmd/dep/testdata/harness_tests/ensure/update/novendor/initial/Gopkg.toml
new file mode 100644
index 0000000000..bbd0a05ba9
--- /dev/null
+++ b/cmd/dep/testdata/harness_tests/ensure/update/novendor/initial/Gopkg.toml
@@ -0,0 +1,4 @@
+
+[[constraint]]
+  name = "github.com/sdboyer/deptest"
+  version = "0.8.0"
diff --git a/cmd/dep/testdata/harness_tests/ensure/update/novendor/initial/main.go b/cmd/dep/testdata/harness_tests/ensure/update/novendor/initial/main.go
new file mode 100644
index 0000000000..e23fcf34c5
--- /dev/null
+++ b/cmd/dep/testdata/harness_tests/ensure/update/novendor/initial/main.go
@@ -0,0 +1,12 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	_ "github.com/sdboyer/deptest"
+)
+
+func main() {
+}
diff --git a/cmd/dep/testdata/harness_tests/ensure/update/novendor/testcase.json b/cmd/dep/testdata/harness_tests/ensure/update/novendor/testcase.json
new file mode 100644
index 0000000000..518f5efbec
--- /dev/null
+++ b/cmd/dep/testdata/harness_tests/ensure/update/novendor/testcase.json
@@ -0,0 +1,5 @@
+{
+  "commands": [
+    ["ensure", "-update", "-no-vendor"]
+  ]
+}