diff --git a/src/cmd/compile/internal/types2/call.go b/src/cmd/compile/internal/types2/call.go
index 34dafce8bf..3377270ef8 100644
--- a/src/cmd/compile/internal/types2/call.go
+++ b/src/cmd/compile/internal/types2/call.go
@@ -479,11 +479,10 @@ func (check *Checker) selector(x *operand, e *syntax.SelectorExpr) {
 			var why string
 			if tpar := asTypeParam(x.typ); tpar != nil {
 				// Type parameter bounds don't specify fields, so don't mention "field".
-				switch obj := tpar.Bound().obj.(type) {
-				case nil:
+				if tname := tpar.Bound().obj; tname != nil {
+					why = check.sprintf("interface %s has no method %s", tname.name, sel)
+				} else {
 					why = check.sprintf("type bound for %s has no method %s", x.typ, sel)
-				case *TypeName:
-					why = check.sprintf("interface %s has no method %s", obj.name, sel)
 				}
 			} else {
 				why = check.sprintf("type %s has no field or method %s", x.typ, sel)
diff --git a/src/cmd/compile/internal/types2/sizeof_test.go b/src/cmd/compile/internal/types2/sizeof_test.go
index 82e1221b67..0b1f7dacad 100644
--- a/src/cmd/compile/internal/types2/sizeof_test.go
+++ b/src/cmd/compile/internal/types2/sizeof_test.go
@@ -28,7 +28,7 @@ func TestSizeof(t *testing.T) {
 		{Tuple{}, 12, 24},
 		{Signature{}, 44, 88},
 		{Union{}, 24, 48},
-		{Interface{}, 44, 88},
+		{Interface{}, 40, 80},
 		{Map{}, 16, 32},
 		{Chan{}, 12, 24},
 		{Named{}, 84, 160},
diff --git a/src/cmd/compile/internal/types2/type.go b/src/cmd/compile/internal/types2/type.go
index 05e6d77d22..f8aa453d5c 100644
--- a/src/cmd/compile/internal/types2/type.go
+++ b/src/cmd/compile/internal/types2/type.go
@@ -264,7 +264,7 @@ func (s *Signature) Variadic() bool { return s.variadic }
 
 // An Interface represents an interface type.
 type Interface struct {
-	obj       Object        // type name object defining this interface; or nil (for better error messages)
+	obj       *TypeName     // corresponding declared object; or nil (for better error messages)
 	methods   []*Func       // ordered list of explicitly declared methods
 	embeddeds []Type        // ordered list of explicitly embedded elements
 	embedPos  *[]syntax.Pos // positions of embedded elements; or nil (for error messages) - use pointer to save space