diff --git a/pkgs/by-name/so/softether/package.nix b/pkgs/by-name/so/softether/package.nix
index e01d86549033..ac3a60810c37 100644
--- a/pkgs/by-name/so/softether/package.nix
+++ b/pkgs/by-name/so/softether/package.nix
@@ -53,6 +53,10 @@ stdenv.mkDerivation (finalAttrs: {
   env.NIX_CFLAGS_COMPILE = toString [
     "-Wno-incompatible-pointer-types"
     "-Wno-implicit-function-declaration"
+
+    # Fix build with gcc15 (-std=gnu23)
+    "-std=gnu17"
+
   ];
 
   meta = {