Index: Sources/Objects/Assembly/cip_as.c
===================================================================
--- Sources/Objects/Assembly/cip_as.c	(revision 109039)
+++ Sources/Objects/Assembly/cip_as.c	(working copy)
@@ -1190,8 +1190,11 @@
   {
     CIP_AS_CONNECTION_LIST_T *ptConnectionEntry;
 
-    if (CIP_AS_IS_RT_FORMAT_RUNIDLE(ptInstance->usParam))
+    if ((CIP_AS_IS_RT_FORMAT_RUNIDLE(ptInstance->usParam)) && (ptInstance->usMaxSize > 0))
     {
+      /* Account additional 4 bytes for the RUN/IDLE header.
+	     Special case: Except for assemblies of size zero (important for ListenOnly/InputOnly producing (heartbeat/dummy) assemblies in the scanner)
+      */
       usAsSize += 4;
     }