diff --git a/pkgs/servers/sql/postgresql/ext/jsonb_deep_sum.nix b/pkgs/servers/sql/postgresql/ext/jsonb_deep_sum.nix
index cf0ba46d8762..092212aa3de0 100644
--- a/pkgs/servers/sql/postgresql/ext/jsonb_deep_sum.nix
+++ b/pkgs/servers/sql/postgresql/ext/jsonb_deep_sum.nix
@@ -16,7 +16,7 @@ stdenv.mkDerivation rec {
   installPhase = ''
     mkdir -p $out/{lib,share/postgresql/extension}
 
-    cp *.so      $out/lib
+    cp *${postgresql.dlSuffix} $out/lib
     cp *.sql     $out/share/postgresql/extension
     cp *.control $out/share/postgresql/extension
   '';