diff --git a/src/cmd/compile/internal/typecheck/expr.go b/src/cmd/compile/internal/typecheck/expr.go
index 24c677e753f..12d1743874c 100644
--- a/src/cmd/compile/internal/typecheck/expr.go
+++ b/src/cmd/compile/internal/typecheck/expr.go
@@ -241,7 +241,7 @@ func tcCompLit(n *ir.CompLitExpr) (res ir.Node) {
 				// walkClosure(), because the instantiated
 				// function is compiled as if in the source
 				// package of the generic function.
-				if !(ir.CurFunc != nil && strings.Index(ir.CurFunc.Nname.Sym().Name, "[") >= 0) {
+				if !(ir.CurFunc != nil && strings.Contains(ir.CurFunc.Nname.Sym().Name, "[")) {
 					if s != nil && !types.IsExported(s.Name) && s.Pkg != types.LocalPkg {
 						base.Errorf("implicit assignment of unexported field '%s' in %v literal", s.Name, t)
 					}