diff --git a/pkgs/development/python-modules/polars/default.nix b/pkgs/development/python-modules/polars/default.nix
index bdd9e72e8290..b4bb2b5ab9cb 100644
--- a/pkgs/development/python-modules/polars/default.nix
+++ b/pkgs/development/python-modules/polars/default.nix
@@ -97,7 +97,7 @@ buildPythonPackage rec {
 
     RUSTFLAGS = lib.concatStringsSep " " (
       lib.optionals (polarsMemoryAllocator.pname == "mimalloc") [
-        "--cfg use_mimalloc"
+        "--cfg allocator=\"mimalloc\""
       ]
     );
     RUST_BACKTRACE = true;