diff --git a/include/unwind.h b/include/unwind.h
index d9a767d..ed01435 100644
--- a/include/unwind.h
+++ b/include/unwind.h
@@ -26,6 +26,10 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.  */
 #ifndef _UNWIND_H
 #define _UNWIND_H
 
+/* uint64_t */
+#include <stdint.h>
+uint64_t x;
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -62,7 +66,7 @@ typedef void (*_Unwind_Exception_Cleanup_Fn) (_Unwind_Reason_Code,
 					      struct _Unwind_Exception *);
 
 typedef _Unwind_Reason_Code (*_Unwind_Stop_Fn) (int, _Unwind_Action,
-						unsigned long,
+						uint64_t,
 						struct _Unwind_Exception *,
 						struct _Unwind_Context *,
 						void *);
@@ -71,14 +75,18 @@ typedef _Unwind_Reason_Code (*_Unwind_Stop_Fn) (int, _Unwind_Action,
    be of type uint64 and the entire structure to be
    double-word-aligned, but that seems a bit overly IA-64-specific.
    Using "unsigned long" instead should give us the desired effect on
-   IA-64, while being more general.  */
+   IA-64, while being more general.
+
+   To be compatible with gcc, exception_class stays 64-bit even on 32-bit machines.
+   See gcc/unwind-generic.h.
+   */
 struct _Unwind_Exception
   {
-    unsigned long exception_class;
+    uint64_t exception_class;
     _Unwind_Exception_Cleanup_Fn exception_cleanup;
     unsigned long private_1;
     unsigned long private_2;
-  };
+  } __attribute__((__aligned__));
 
 extern _Unwind_Reason_Code _Unwind_RaiseException (struct _Unwind_Exception *);
 extern _Unwind_Reason_Code _Unwind_ForcedUnwind (struct _Unwind_Exception *,
diff --git a/src/unwind/RaiseException.c b/src/unwind/RaiseException.c
index 5533876..66a681d 100644
--- a/src/unwind/RaiseException.c
+++ b/src/unwind/RaiseException.c
@@ -28,7 +28,7 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.  */
 PROTECTED _Unwind_Reason_Code
 _Unwind_RaiseException (struct _Unwind_Exception *exception_object)
 {
-  unsigned long exception_class = exception_object->exception_class;
+  uint64_t exception_class = exception_object->exception_class;
   _Unwind_Personality_Fn personality;
   struct _Unwind_Context context;
   _Unwind_Reason_Code reason;
diff --git a/src/unwind/unwind-internal.h b/src/unwind/unwind-internal.h
index 169bad5..130cb81 100644
--- a/src/unwind/unwind-internal.h
+++ b/src/unwind/unwind-internal.h
@@ -38,7 +38,7 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.  */
 #define _U_VERSION	1
 
 typedef _Unwind_Reason_Code (*_Unwind_Personality_Fn)
-	(int, _Unwind_Action, unsigned long, struct _Unwind_Exception *,
+	(int, _Unwind_Action, uint64_t, struct _Unwind_Exception *,
 	 struct _Unwind_Context *);
 
 struct _Unwind_Context {
@@ -59,7 +59,7 @@ _Unwind_Phase2 (struct _Unwind_Exception *exception_object,
 		struct _Unwind_Context *context)
 {
   _Unwind_Stop_Fn stop = (_Unwind_Stop_Fn) exception_object->private_1;
-  unsigned long exception_class = exception_object->exception_class;
+  uint64_t exception_class = exception_object->exception_class;
   void *stop_parameter = (void *) exception_object->private_2;
   _Unwind_Personality_Fn personality;
   _Unwind_Reason_Code reason;