diff --git a/manifold/CMakeLists.txt b/manifold/CMakeLists.txt
index 9dae1d01..b1012a7e 100644
--- a/manifold/CMakeLists.txt
+++ b/manifold/CMakeLists.txt
@@ -14,7 +14,7 @@ if (ENABLE_MANIFOLD)
   ExternalProject_Add(MANIFOLD_BLD
     URL "${CMAKE_CURRENT_SOURCE_DIR}/manifold"
     BUILD_ALWAYS ${EXT_BUILD_ALWAYS} ${LOG_OPTS}
-    #PATCH_COMMAND ${PATCH_EXECUTABLE};-E;-p1;${PATCH_OPTIONS};-i;${CMAKE_CURRENT_SOURCE_DIR}/manifold.patch
+    PATCH_COMMAND ${PATCH_EXECUTABLE};-E;-p1;${PATCH_OPTIONS};-i;${CMAKE_CURRENT_SOURCE_DIR}/manifold.patch
     CMAKE_ARGS
     ${BUILD_TYPE_SPECIFIER}
     $<$<BOOL:${ZLIB_TARGET}>:-DZ_PREFIX=ON>
diff --git a/manifold/manifold.patch b/manifold/manifold.patch
new file mode 100644
index 00000000..6f42eb5c
--- /dev/null
+++ b/manifold/manifold.patch
@@ -0,0 +1,12 @@
+diff -Naur manifold/src/utilities/include/optional_assert.h MANIFOLD_BLD/src/utilities/include/optional_assert.h
+--- manifold/src/utilities/include/optional_assert.h	2024-07-02 20:09:19.078438473 -0400
++++ MANIFOLD_BLD/src/utilities/include/optional_assert.h	2024-07-09 16:59:17.609083445 -0400
+@@ -15,7 +15,7 @@
+ #pragma once
+ 
+ #include "public.h"
+-#if MANIFOLD_EXCEPTIONS
++#ifdef MANIFOLD_EXCEPTIONS
+ #include <stdexcept>
+ #endif
+