diff --git a/lib/msf/core/exploit/http/server.rb b/lib/msf/core/exploit/http/server.rb
index fca138e310..16a7b4e89a 100644
--- a/lib/msf/core/exploit/http/server.rb
+++ b/lib/msf/core/exploit/http/server.rb
@@ -798,7 +798,7 @@ protected
 	# publication on "DEPS – Precise Heap Spray on Firefox and IE10".
 	#
 	# The "sprayHeap" JavaScript function supports the following arguments:
-	#   shellcode     => The shellcode to spray in JavaScript.
+	#   shellcode     => The shellcode to spray in JavaScript.  Note: Avoid null bytes.
 	#   objId         => Optional. The ID for a <div> HTML tag.
 	#   offset        => Optional. Number of bytes to align the shellcode, default: 0x104
 	#   heapBlockSize => Optional. Allocation size, default: 0x80000