diff --git a/OpenEXR/IlmImf/ImfDwaCompressor.cpp b/OpenEXR/IlmImf/ImfDwaCompressor.cpp
index 8dc0885e42..fb359aae8e 100644
--- a/OpenEXR/IlmImf/ImfDwaCompressor.cpp
+++ b/OpenEXR/IlmImf/ImfDwaCompressor.cpp
@@ -2422,7 +2422,7 @@ DwaCompressor::uncompress
         unsigned short ruleSize = 0;
         Xdr::read<CharPtrIO>(dataPtr, ruleSize);
 
-        if (ruleSize < 0) 
+        if (ruleSize < Xdr::size<unsigned short>() ) 
             throw IEX_NAMESPACE::InputExc("Error uncompressing DWA data"
                                 " (corrupt header file).");