diff --git a/src/cmd/go/go_test.go b/src/cmd/go/go_test.go
index 5727eb094e..f26c3660e4 100644
--- a/src/cmd/go/go_test.go
+++ b/src/cmd/go/go_test.go
@@ -3787,3 +3787,26 @@ GLOBL ·constants<>(SB),8,$8
 	tg.setenv("GOPATH", tg.path("go"))
 	tg.run("build", "p")
 }
+
+// Issue 18778.
+func TestDotDotDotOutsideGOPATH(t *testing.T) {
+	tg := testgo(t)
+	defer tg.cleanup()
+
+	tg.tempFile("pkgs/a.go", `package x`)
+	tg.tempFile("pkgs/a_test.go", `package x_test
+import "testing"
+func TestX(t *testing.T) {}`)
+
+	tg.tempFile("pkgs/a/a.go", `package a`)
+	tg.tempFile("pkgs/a/a_test.go", `package a_test
+import "testing"
+func TestA(t *testing.T) {}`)
+
+	tg.cd(tg.path("pkgs"))
+	tg.run("build", "./...")
+	tg.run("test", "./...")
+	tg.run("list", "./...")
+	tg.grepStdout("pkgs$", "expected package not listed")
+	tg.grepStdout("pkgs/a", "expected package not listed")
+}
diff --git a/src/cmd/go/pkg.go b/src/cmd/go/pkg.go
index d69fa5118f..e40f9420c7 100644
--- a/src/cmd/go/pkg.go
+++ b/src/cmd/go/pkg.go
@@ -429,7 +429,7 @@ func setErrorPos(p *Package, importPos []token.Position) *Package {
 func cleanImport(path string) string {
 	orig := path
 	path = pathpkg.Clean(path)
-	if strings.HasPrefix(orig, "./") && path != ".." && path != "." && !strings.HasPrefix(path, "../") {
+	if strings.HasPrefix(orig, "./") && path != ".." && !strings.HasPrefix(path, "../") {
 		path = "./" + path
 	}
 	return path