diff --git a/tool/DataTypeHandler.cpp b/tool/DataTypeHandler.cpp
index f255f681..e119daaa 100644
--- a/tool/DataTypeHandler.cpp
+++ b/tool/DataTypeHandler.cpp
@@ -186,9 +186,10 @@ size_t DataTypeHandler::interpretAsType(
         case 0x000a: // octet_string
         case 0x000b: // unicode_string
             dataSize = str.str().size();
-            if (dataSize >= targetSize) {
+            if (dataSize > targetSize) {
                 stringstream err;
-                err << "String too large";
+                err << "String too large ("
+                    << dataSize << " > " << targetSize << ")";
                 throw SizeException(err.str());
             }
             str >> (char *) target;