diff --git a/pkgs/servers/mail/mlmmj/default.nix b/pkgs/servers/mail/mlmmj/default.nix
index 89e142b04f9..aba0664b8f4 100644
--- a/pkgs/servers/mail/mlmmj/default.nix
+++ b/pkgs/servers/mail/mlmmj/default.nix
@@ -10,6 +10,12 @@ stdenv.mkDerivation rec {
     sha256 = "1sghqvwizvm1a9w56r34qy5njaq1c26bagj85r60h32gh3fx02bn";
   };
 
+  configureFlags = lib.optionals (stdenv.hostPlatform != stdenv.buildPlatform) [
+    # AC_FUNC_MALLOC is broken on cross builds.
+    "ac_cv_func_malloc_0_nonnull=yes"
+    "ac_cv_func_realloc_0_nonnull=yes"
+  ];
+
   # Workaround build failure on -fno-common toolchains like upstream
   # gcc-10. Otherwise build fails as:
   #   ld: getlistdelim.o:/build/mlmmj-1.3.0/src/../include/mlmmj.h:84: multiple definition of