diff --git a/helper/resource/testing.go b/helper/resource/testing.go
index 90cfc175fa..43a59e93c0 100644
--- a/helper/resource/testing.go
+++ b/helper/resource/testing.go
@@ -230,6 +230,16 @@ func testStep(
 		}
 	}
 
+	// Verify that Plan is now empty and we don't have a perpetual diff issue
+	if p, err := ctx.Plan(); err != nil {
+		return state, fmt.Errorf("Error on follow-up plan: %s", err)
+	} else {
+		if p.Diff != nil && !p.Diff.Empty() {
+			return state, fmt.Errorf(
+				"After applying this step, the plan was not empty:\n\n%s", p)
+		}
+	}
+
 	return state, err
 }
 
diff --git a/helper/resource/testing_test.go b/helper/resource/testing_test.go
index cf51c7b223..2f7ed0517f 100644
--- a/helper/resource/testing_test.go
+++ b/helper/resource/testing_test.go
@@ -18,6 +18,8 @@ func init() {
 
 func TestTest(t *testing.T) {
 	mp := testProvider()
+	mp.DiffReturn = nil
+
 	mp.ApplyReturn = &terraform.InstanceState{
 		ID: "foo",
 	}