diff --git a/pkgs/by-name/ca/casacore/package.nix b/pkgs/by-name/ca/casacore/package.nix
index 5a026b41ba10..13323464fef4 100644
--- a/pkgs/by-name/ca/casacore/package.nix
+++ b/pkgs/by-name/ca/casacore/package.nix
@@ -101,6 +101,10 @@ stdenv.mkDerivation (finalAttrs: {
     (lib.cmakeBool "PORTABLE" true)
     (lib.cmakeBool "USE_PCH" false)
     (lib.cmakeBool "BUILD_FFTPACK_DEPRECATED" true) # Needed for casacpp
+  ]
+  ++ lib.optionals stdenv.hostPlatform.isDarwin [
+    # Upstream probes this flag, but it fails on darwin, so pass it explicitly
+    (lib.cmakeFeature "CMAKE_Fortran_FLAGS" "-fallow-argument-mismatch")
   ];
 
   meta = {