diff --git a/Utilities/GCDMulticastDelegate.m b/Utilities/GCDMulticastDelegate.m
index 1785c274d4..c48ec32010 100644
--- a/Utilities/GCDMulticastDelegate.m
+++ b/Utilities/GCDMulticastDelegate.m
@@ -396,6 +396,12 @@ - (NSInvocation *)duplicateInvocation:(NSInvocation *)origInvocation
 			[origInvocation getArgument:&value atIndex:i];
 			[dupInvocation setArgument:&value atIndex:i];
 		}
+        else if (*type == ':')
+        {
+            void *value;
+            [origInvocation getArgument:&value atIndex:i];
+            [dupInvocation setArgument:&value atIndex:i];
+        }
 		else if (*type == '^')
 		{
 			void *block;