diff --git a/pkgs/by-name/li/lingeling/gcc-15.patch b/pkgs/by-name/li/lingeling/gcc-15.patch
new file mode 100644
index 000000000000..e09230bd1889
--- /dev/null
+++ b/pkgs/by-name/li/lingeling/gcc-15.patch
@@ -0,0 +1,58 @@
+From f1e35d1102a87eb576ce3f09da5cdf1d4b09722c Mon Sep 17 00:00:00 2001
+From: Anders Kaseorg <andersk@mit.edu>
+Date: Thu, 1 Jan 2026 21:50:52 -0800
+Subject: [PATCH] Fix incompatible pointer type errors from GCC 15
+
+Signed-off-by: Anders Kaseorg <andersk@mit.edu>
+---
+ treengeling.c | 16 +++++++++++++---
+ 1 file changed, 13 insertions(+), 3 deletions(-)
+
+diff --git a/treengeling.c b/treengeling.c
+index 1fcafc8..c26c5b5 100644
+--- a/treengeling.c
++++ b/treengeling.c
+@@ -292,6 +292,16 @@ UNLOCK (simplified)
+ UNLOCK (stats)
+ UNLOCK (workers)
+ 
++static void lockmsg_callback (void * voidptr) {
++  lockmsg();
++  (void) voidptr;
++}
++
++static void unlockmsg_callback (void * voidptr) {
++  unlockmsg();
++  (void) voidptr;
++}
++
+ /*------------------------------------------------------------------------*/
+ 
+ static void err (const char * fmt, ...) {
+@@ -818,7 +828,7 @@ static void initroot () {
+     lglsetopt (root, "bca", 0);
+     lglseterm (root, term, 0);
+     lglsetconsumeunits (root, consumeunits, &rootconsumed);
+-    lglsetmsglock (root, lockmsg, unlockmsg, 0);
++    lglsetmsglock (root, lockmsg_callback, unlockmsg_callback, 0);
+   }
+   lglsetime (root, getime);
+   lglsetprefix (root, "c (root) ");
+@@ -857,7 +867,7 @@ static Node * newnode (Node * parent, int decision) {
+   sprintf (prefix, "c (%d %lld) ", res->depth, (LL) res->id);
+   lglsetprefix (res->lgl, prefix);
+   lglseterm (res->lgl, term, 0);
+-  lglsetmsglock (res->lgl, lockmsg, unlockmsg, 0);
++  lglsetmsglock (res->lgl, lockmsg_callback, unlockmsg_callback, 0);
+   if (!noparallel) lglsetconsumeunits (res->lgl, consumeunits, &res->consumed);
+   cubemsg (res, "opened cube");
+   added++;
+@@ -1040,7 +1050,7 @@ static void startparallel (LGL * lgl) {
+   lglseterm (parallel.lgl, term, 0);
+   lglsetproduceunit (parallel.lgl, produceunit, 0);
+   lglsetconsumecls (parallel.lgl, consumecls, 0);
+-  lglsetmsglock (parallel.lgl, lockmsg, unlockmsg, 0);
++  lglsetmsglock (parallel.lgl, lockmsg_callback, unlockmsg_callback, 0);
+   parallel.decisions = lglgetdecs (parallel.lgl);
+   parallel.conflicts = lglgetconfs (parallel.lgl);
+   parallel.propagations = lglgetprops (parallel.lgl);
diff --git a/pkgs/by-name/li/lingeling/package.nix b/pkgs/by-name/li/lingeling/package.nix
index ee5816caa73f..898601d0693d 100644
--- a/pkgs/by-name/li/lingeling/package.nix
+++ b/pkgs/by-name/li/lingeling/package.nix
@@ -17,6 +17,12 @@ stdenv.mkDerivation {
     sha256 = "1lb2g37nd8qq5hw5g6l691nx5095336yb2zlbaw43mg56hkj8357";
   };
 
+  patches = [
+    # Fix incompatible pointer type errors from GCC 15
+    # https://github.com/arminbiere/lingeling/pull/11
+    ./gcc-15.patch
+  ];
+
   configurePhase = ''
     runHook preConfigure