diff --git a/src/net/http/request.go b/src/net/http/request.go
index 7f473dd15d..c493aeb2d7 100644
--- a/src/net/http/request.go
+++ b/src/net/http/request.go
@@ -333,9 +333,11 @@ func (r *Request) WithContext(ctx context.Context) *Request {
 	// Deep copy the URL because it isn't
 	// a map and the URL is mutable by users
 	// of WithContext.
-	r2URL := new(url.URL)
-	*r2URL = *r.URL
-	r2.URL = r2URL
+	if r.URL != nil {
+		r2URL := new(url.URL)
+		*r2URL = *r.URL
+		r2.URL = r2URL
+	}
 
 	return r2
 }
diff --git a/src/net/http/request_test.go b/src/net/http/request_test.go
index 1608d1c4fe..967156bac9 100644
--- a/src/net/http/request_test.go
+++ b/src/net/http/request_test.go
@@ -799,6 +799,13 @@ func TestWithContextDeepCopiesURL(t *testing.T) {
 	if firstURL == secondURL {
 		t.Errorf("unexpected change to original request's URL")
 	}
+
+	// And also check we don't crash on nil (Issue 20601)
+	req.URL = nil
+	reqCopy = req.WithContext(context.Background())
+	if reqCopy.URL != nil {
+		t.Error("expected nil URL in cloned request")
+	}
 }
 
 // verify that NewRequest sets Request.GetBody and that it works