diff --git a/src/cmd/go/testdata/script/src_file.txt b/src/cmd/go/testdata/script/src_file.txt
new file mode 100644
index 0000000000..8d5c20bc97
--- /dev/null
+++ b/src/cmd/go/testdata/script/src_file.txt
@@ -0,0 +1,9 @@
+# Files in src should not be treated as packages
+
+exists $GOROOT/src/regexp/testdata/README
+go list -f '{{.Dir}}' regexp/testdata/README
+
+-- go.mod --
+module regexp/testdata/README
+-- p.go --
+package p
diff --git a/src/internal/goroot/gc.go b/src/internal/goroot/gc.go
index 79403d29fc..c0216f4ea5 100644
--- a/src/internal/goroot/gc.go
+++ b/src/internal/goroot/gc.go
@@ -20,8 +20,8 @@ func IsStandardPackage(goroot, compiler, path string) bool {
 	switch compiler {
 	case "gc":
 		dir := filepath.Join(goroot, "src", path)
-		_, err := os.Stat(dir)
-		return err == nil
+		info, err := os.Stat(dir)
+		return err == nil && info.IsDir()
 	case "gccgo":
 		return gccgoSearch.isStandard(path)
 	default: