diff --git a/pkgs/development/ocaml-modules/patricia-tree/default.nix b/pkgs/development/ocaml-modules/patricia-tree/default.nix
index d61c28c166a5..a3f548664a5d 100644
--- a/pkgs/development/ocaml-modules/patricia-tree/default.nix
+++ b/pkgs/development/ocaml-modules/patricia-tree/default.nix
@@ -1,5 +1,6 @@
 {
   lib,
+  ocaml,
   buildDunePackage,
   fetchFromGitHub,
   findlib,
@@ -14,6 +15,11 @@ buildDunePackage rec {
 
   minimalOCamlVersion = "4.14";
 
+  # Fix build with gcc15
+  env = lib.optionalAttrs (lib.versions.majorMinor ocaml.version == "5.0") {
+    NIX_CFLAGS_COMPILE = "-std=gnu11";
+  };
+
   src = fetchFromGitHub {
     owner = "codex-semantics-library";
     repo = "patricia-tree";