diff --git a/pkgs/development/tools/rust/cargo-pgrx/buildPgrxExtension.nix b/pkgs/development/tools/rust/cargo-pgrx/buildPgrxExtension.nix
index b4cbb95150a7..7138ae8ecfef 100644
--- a/pkgs/development/tools/rust/cargo-pgrx/buildPgrxExtension.nix
+++ b/pkgs/development/tools/rust/cargo-pgrx/buildPgrxExtension.nix
@@ -119,7 +119,7 @@ let
 
       NIX_PGLIBDIR="${postgresql}/lib" \
       PGRX_BUILD_FLAGS="--frozen -j $NIX_BUILD_CORES ${builtins.concatStringsSep " " cargoBuildFlags}" \
-      RUSTFLAGS="${lib.optionalString stdenv.isDarwin "-Clink-args=-Wl,-undefined,dynamic_lookup"}" \
+      ${lib.optionalString stdenv.isDarwin ''RUSTFLAGS="''${RUSTFLAGS:+''${RUSTFLAGS} }-Clink-args=-Wl,-undefined,dynamic_lookup"''} \
       cargo pgrx package \
         --pg-config ${postgresql}/bin/pg_config \
         ${maybeDebugFlag} \