diff --git a/patches/mingw/clang-cpuidex.patch b/patches/mingw/clang-cpuidex.patch
new file mode 100644
index 0000000..3ff868a
--- /dev/null
+++ b/patches/mingw/clang-cpuidex.patch
@@ -0,0 +1,13 @@
+diff --git a/include/psdk_inc/intrin-impl.h b/include/psdk_inc/intrin-impl.h
+index 0267f93a2..0c9db2e6a 100644
+--- a/include/psdk_inc/intrin-impl.h
++++ b/include/psdk_inc/intrin-impl.h
+@@ -2016,7 +2016,7 @@ void __cpuid(int CPUInfo[4], int InfoType) {
+ #define __INTRINSIC_DEFINED___cpuid
+ #endif /* __INTRINSIC_PROLOG */
+ 
+-#if (!defined(__GNUC__) || __GNUC__ < 11)
++#if (!defined(__GNUC__) || __GNUC__ < 11) && !defined(__clang__)
+ #if __INTRINSIC_PROLOG(__cpuidex)
+ void __cpuidex(int CPUInfo[4], int, int);
+ #if !__has_builtin(__cpuidex)
diff --git a/scripts/release/windows_x64/p2pool_windows_x64.sh b/scripts/release/windows_x64/p2pool_windows_x64.sh
index 0187c70..ff599e0 100755
--- a/scripts/release/windows_x64/p2pool_windows_x64.sh
+++ b/scripts/release/windows_x64/p2pool_windows_x64.sh
@@ -26,6 +26,14 @@ flags_datetime="-D__DATE__=\"\\\"$CURRENT_DATE\\\"\" -D__TIME__=\"\\\"$CURRENT_T
 MINGW_SYSROOT="$(x86_64-w64-mingw32-g++ -print-sysroot)"
 flags_sysroot="--sysroot=$MINGW_SYSROOT"
 
+# Fix mingw-w64 headers for clang: skip redefining __cpuidex when clang already
+# provides one via its cpuid.h.
+if [ -f "$PATCH_DIR/mingw/clang-cpuidex.patch" ]; then
+	cd "$MINGW_SYSROOT"
+	patch -N -p1 < "$PATCH_DIR/mingw/clang-cpuidex.patch" || true
+	cd /p2pool
+fi
+
 flags_libs="--target=x86_64-pc-windows-gnu $flags_sysroot -Os -flto -Wl,/timestamp:$BUILD_TIMESTAMP -fuse-ld=lld -w $flags_size $flags_datetime"
 
 flags_p2pool="--target=x86_64-pc-windows-gnu $flags_sysroot -Wl,/timestamp:$BUILD_TIMESTAMP -fuse-ld=lld -femulated-tls -Wno-unused-command-line-argument -Wno-unknown-attributes $flags_size $flags_datetime"