diff --git a/pkgs/by-name/op/openctm/package.nix b/pkgs/by-name/op/openctm/package.nix
index 4d380543857f..d89640ca8210 100644
--- a/pkgs/by-name/op/openctm/package.nix
+++ b/pkgs/by-name/op/openctm/package.nix
@@ -13,7 +13,7 @@ stdenv.mkDerivation (finalAttrs: {
   version = "1.0.3";
 
   src = fetchurl {
-    url = "https://downloads.sourceforge.net/project/openctm/OpenCTM-${finalAttrs.version}/OpenCTM-${finalAttrs.version}-src.tar.bz2";
+    url = "mirror://sourceforge/project/openctm/OpenCTM-${finalAttrs.version}/OpenCTM-${finalAttrs.version}-src.tar.bz2";
     hash = "sha256-So0mCNlzZPfuxWt8Y3xWuTCK6YKGs+kNu3QTyQ6UPx0=";
   };