diff --git a/terraform/semantics_test.go b/terraform/semantics_test.go
index 8c1867c488..46346f2d36 100644
--- a/terraform/semantics_test.go
+++ b/terraform/semantics_test.go
@@ -9,36 +9,42 @@ import (
 func TestSMCUserVariables(t *testing.T) {
 	c := testModule(t, "smc-uservars")
 
-	// Required variables not set
+	// No variables set
 	diags := checkInputVariables(c.Module.Variables, nil)
 	if !diags.HasErrors() {
 		t.Fatal("check succeeded, but want errors")
 	}
 
 	// Required variables set, optional variables unset
+	// This is still an error at this layer, since it's the caller's
+	// responsibility to have already merged in any default values.
 	diags = checkInputVariables(c.Module.Variables, InputValues{
 		"foo": &InputValue{
 			Value:      cty.StringVal("bar"),
 			SourceType: ValueFromCLIArg,
 		},
 	})
-	if diags.HasErrors() {
-		t.Fatalf("unexpected errors: %s", diags.Err())
+	if !diags.HasErrors() {
+		t.Fatal("check succeeded, but want errors")
 	}
 
-	// Mapping complete override
+	// All variables set
 	diags = checkInputVariables(c.Module.Variables, InputValues{
 		"foo": &InputValue{
 			Value:      cty.StringVal("bar"),
 			SourceType: ValueFromCLIArg,
 		},
-		"map": &InputValue{
+		"bar": &InputValue{
 			Value:      cty.StringVal("baz"),
 			SourceType: ValueFromCLIArg,
 		},
+		"map": &InputValue{
+			Value:      cty.StringVal("baz"), // okay because config has no type constraint
+			SourceType: ValueFromCLIArg,
+		},
 	})
-	if !diags.HasErrors() {
-		t.Fatal("check succeeded, but want errors")
+	if diags.HasErrors() {
+		//t.Fatal("check succeeded, but want errors")
+		t.Fatalf("unexpected errors: %s", diags.Err())
 	}
-
 }