diff --git a/trace_proto.go b/trace_proto.go
index 2d259cf..f64ab1e 100644
--- a/trace_proto.go
+++ b/trace_proto.go
@@ -17,6 +17,7 @@ package stackdriver
 import (
 	"fmt"
 	"math"
+	"strconv"
 	"time"
 	"unicode/utf8"
 
@@ -234,6 +235,13 @@ func attributeValue(v interface{}) *tracepb.AttributeValue {
 		return &tracepb.AttributeValue{
 			Value: &tracepb.AttributeValue_IntValue{IntValue: value},
 		}
+	case float64:
+		// TODO: set double value if Stackdriver Trace support it in the future.
+		return &tracepb.AttributeValue{
+			Value: &tracepb.AttributeValue_StringValue{
+				StringValue: trunc(strconv.FormatFloat(value, 'f', -1, 64),
+					maxAttributeStringValue)},
+		}
 	case string:
 		return &tracepb.AttributeValue{
 			Value: &tracepb.AttributeValue_StringValue{StringValue: trunc(value, maxAttributeStringValue)},
diff --git a/trace_proto_test.go b/trace_proto_test.go
index 45256be..8eb7b51 100644
--- a/trace_proto_test.go
+++ b/trace_proto_test.go
@@ -76,7 +76,11 @@ func generateSpan() {
 			span2.AddAttributes(
 				trace.StringAttribute("key1", "value1"),
 				trace.StringAttribute("key2", "value2"))
-			span2.AddAttributes(trace.Int64Attribute("key1", 100))
+			span2.AddAttributes(
+				trace.Int64Attribute("key1", 100),
+				// TODO [rghetia]: uncomment the test case after go.opencensus.io/trace@v0.20.0 is released.
+				//trace.Float64Attribute("key3", 100.001),
+			)
 			span2.End()
 		}
 		{
@@ -130,8 +134,10 @@ func createExpectedSpans() spans {
 			DisplayName: trunc("span2", 128),
 			Attributes: &tracepb.Span_Attributes{
 				AttributeMap: map[string]*tracepb.AttributeValue{
-					"key2":     {Value: &tracepb.AttributeValue_StringValue{StringValue: trunc("value2", 256)}},
-					"key1":     {Value: &tracepb.AttributeValue_IntValue{IntValue: 100}},
+					"key2": {Value: &tracepb.AttributeValue_StringValue{StringValue: trunc("value2", 256)}},
+					"key1": {Value: &tracepb.AttributeValue_IntValue{IntValue: 100}},
+					// TODO [rghetia]: uncomment the test case after go.opencensus.io/trace@v0.20.0 is released.
+					//"key3": {Value: &tracepb.AttributeValue_StringValue{StringValue: trunc("100.001", 256)}},
 					agentLabel: {Value: &tracepb.AttributeValue_StringValue{StringValue: ua}},
 				},
 			},