diff --git a/pkgs/by-name/ri/river-tag-overlay/package.nix b/pkgs/by-name/ri/river-tag-overlay/package.nix
index 69d950312bb5..f4e409a41326 100644
--- a/pkgs/by-name/ri/river-tag-overlay/package.nix
+++ b/pkgs/by-name/ri/river-tag-overlay/package.nix
@@ -3,6 +3,7 @@
   stdenv,
   fetchFromSourcehut,
   fetchpatch,
+  fetchpatch2,
   wayland,
   pixman,
   pkg-config,
@@ -26,6 +27,11 @@ stdenv.mkDerivation (finalAttrs: {
       url = "https://git.sr.ht/~leon_plickat/river-tag-overlay/commit/791eaadf46482121a4c811ffba13d03168d74d8f.patch";
       sha256 = "CxSDcweHGup1EF3oD/2vhP6RFoeYorj0BwmlgA3tbPE=";
     })
+    # Specify argument types for C23 compatibility (gcc 15).
+    (fetchpatch2 {
+      url = "https://git.sr.ht/~leon_plickat/river-tag-overlay/commit/b7d9232f9106c6d2c3ecce802495f14069ce3406.patch";
+      hash = "sha256-/fNpVPY09zwwymS/VNaonqX7jtdflC3Iot5R26VsTTw=";
+    })
   ];
 
   buildInputs = [