diff --git a/pkgs/by-name/ma/mautrix-signal/package.nix b/pkgs/by-name/ma/mautrix-signal/package.nix
index 8d05f31cf4ac..fbdb9cf03a8e 100644
--- a/pkgs/by-name/ma/mautrix-signal/package.nix
+++ b/pkgs/by-name/ma/mautrix-signal/package.nix
@@ -42,7 +42,9 @@ buildGoModule rec {
 
   tags = lib.optional withGoolm "goolm";
 
-  CGO_LDFLAGS = lib.optional withGoolm [ cppStdLib ];
+  env = lib.optionalAttrs withGoolm {
+    CGO_LDFLAGS = toString [ cppStdLib ];
+  };
 
   vendorHash = "sha256-TFz5P8czj8J9+QTFHjffCldw8Je2+DiM49W7jv5rY/I=";