Is there any reason why using an NSMutableDictionary would crash NSNotificationCenter?

Question

When posting notifications with NSNotificationCenter, is there any reason why passing in a NSMutableDictionary instead of an NSDictionary as the userInfo could cause a crash?

- (void)postNotificationName:(NSString *)aName object:(id)anObject userInfo:(NSDictionary *)aUserInfo;

I'm seeing the following crash log:

 Exception Type:  SIGSEGV
 Exception Codes: SEGV_ACCERR at 0xffffffffe0000008
0   libobjc.A.dylib                     0x31516fbc objc_msgSend + 16
1   Foundation                          0x3195b50f __57-[NSNotificationCenter addObserver:selector:name:object:]_block_invoke_0 + 19
2   CoreFoundation                      0x37a02577 ___CFXNotificationPost_block_invoke_0 + 71
3   CoreFoundation                      0x3798e0cf _CFXNotificationPost + 1407
4   Foundation                          0x318cf3fb -[NSNotificationCenter postNotificationName:object:userInfo:] + 67