diff --git a/pkgs/by-name/li/libx86emu/package.nix b/pkgs/by-name/li/libx86emu/package.nix
index caea4869f04d..ada07a372ae9 100644
--- a/pkgs/by-name/li/libx86emu/package.nix
+++ b/pkgs/by-name/li/libx86emu/package.nix
@@ -29,6 +29,9 @@ stdenv.mkDerivation rec {
     "shared"
     "CC=${stdenv.cc.targetPrefix}cc"
   ];
+
+  NIX_CFLAGS_COMPILE = "-Wno-implicit-function-declaration";
+
   enableParallelBuilding = true;
 
   installFlags = [