diff --git a/third_party/libunwind/README.cosmo b/third_party/libunwind/README.cosmo
index 3524d2a39..e74e838c3 100644
--- a/third_party/libunwind/README.cosmo
+++ b/third_party/libunwind/README.cosmo
@@ -11,3 +11,6 @@ ORIGIN
   Author: Tobias Hieta <tobias@hieta.se>
   Date:   Tue, 28 Nov 2023 09:52:28 +0100
 
+LOCAL CHANGES
+  - Fixed `_Unwind_FunctionContext` struct to be ABI-compatible with code
+  generated by GCC.
diff --git a/third_party/libunwind/Unwind-sjlj.c b/third_party/libunwind/Unwind-sjlj.c
index ae8b73351..514358e5b 100644
--- a/third_party/libunwind/Unwind-sjlj.c
+++ b/third_party/libunwind/Unwind-sjlj.c
@@ -28,6 +28,8 @@
 
 #if defined(_LIBUNWIND_BUILD_SJLJ_APIS)
 
+typedef uintptr_t _Unwind_Word __attribute__((__mode__(__unwind_word__)));
+
 struct _Unwind_FunctionContext {
   // next function in stack of handlers
   struct _Unwind_FunctionContext *prev;
@@ -47,7 +49,7 @@ struct _Unwind_FunctionContext {
   uint32_t                        resumeLocation;
 
   // set by personality handler to be parameters passed to landing pad function
-  uint32_t                        resumeParameters[4];
+  _Unwind_Word                    resumeParameters[4];
 #endif
 
   // set by calling function before registering