diff --git a/pkgs/by-name/ti/timidity/package.nix b/pkgs/by-name/ti/timidity/package.nix
index 73300dfa3cd5..1d26190c5b52 100644
--- a/pkgs/by-name/ti/timidity/package.nix
+++ b/pkgs/by-name/ti/timidity/package.nix
@@ -99,6 +99,9 @@ stdenv.mkDerivation rec {
     sed -i 's/^\(calcnewt\$(EXEEXT):\).*/\1/g' timidity/Makefile
   '';
 
+  # Fix build with gcc15
+  env.NIX_CFLAGS_COMPILE = "-std=gnu17";
+
   # the instruments could be compressed (?)
   postInstall = ''
     mkdir -p $out/share/timidity/;