diff --git a/src/net/udpsock_test.go b/src/net/udpsock_test.go
index 518c66c3314..9fe74f47a2b 100644
--- a/src/net/udpsock_test.go
+++ b/src/net/udpsock_test.go
@@ -475,6 +475,17 @@ func TestUDPReadTimeout(t *testing.T) {
 }
 
 func TestAllocs(t *testing.T) {
+	switch runtime.GOOS {
+	case "plan9":
+		// Plan9 wasn't optimized.
+		t.Skipf("skipping on %v", runtime.GOOS)
+	}
+	builder := os.Getenv("GO_BUILDER_NAME")
+	switch builder {
+	case "linux-amd64-noopt":
+		// Optimizations are required to remove the allocs.
+		t.Skipf("skipping on %v", builder)
+	}
 	conn, err := ListenUDP("udp4", &UDPAddr{IP: IPv4(127, 0, 0, 1)})
 	if err != nil {
 		t.Fatal(err)