diff --git a/src/pkg/strings/strings_test.go b/src/pkg/strings/strings_test.go
index 5308e8b7e41..957af67b2ba 100644
--- a/src/pkg/strings/strings_test.go
+++ b/src/pkg/strings/strings_test.go
@@ -527,7 +527,7 @@ func TestTrim(t *testing.T) {
 		case "TrimRight":
 			f = TrimRight
 		default:
-			t.Error("Undefined trim function %s", name)
+			t.Errorf("Undefined trim function %s", name)
 		}
 		actual := f(tc.in, tc.cutset)
 		if actual != tc.out {