diff --git a/Source/MemoryStream.m b/Source/MemoryStream.m
index 2841c4bb9..9a1b3c98a 100644
--- a/Source/MemoryStream.m
+++ b/Source/MemoryStream.m
@@ -95,6 +95,14 @@ static BOOL debug_memory_stream = NO;
 	       prefix:p position:i];
 }
 
+- initWithCapacity: (unsigned)capacity
+	    prefix: (unsigned)p
+{
+  return [self initWithSize: capacity
+	       prefix: p
+	       position: 0];
+}
+
 - initWithCapacity: (unsigned)capacity
 {
   return [self initWithSize:capacity prefix:0 position:0];