diff --git a/pkgs/tools/security/snow/default.nix b/pkgs/tools/security/snow/default.nix
index dbea144cb1ba..5e7cb013a4ed 100644
--- a/pkgs/tools/security/snow/default.nix
+++ b/pkgs/tools/security/snow/default.nix
@@ -9,7 +9,9 @@ stdenv.mkDerivation rec {
     sha256 = "0r9q45y55z4i0askkxmxrx0jr1620ypd870vz0hx2a6n9skimdy0";
   };
 
-  makeFlags = [ "CFLAGS=-O2" ];
+  preBuild = ''
+    makeFlagsArray+=(CFLAGS="-O2 -std=c89")
+  '';
 
   installPhase = ''
     install -Dm755 snow -t $out/bin