diff --git a/VERSION b/VERSION
index 137ac1e..4b0033d 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-1.5.203
+1.5.204
diff --git a/base/flatten.c b/base/flatten.c
index f21c807..5b3f610 100644
--- a/base/flatten.c
+++ b/base/flatten.c
@@ -259,13 +259,16 @@ int flattenInstancesOf(char *name, int fnum, char *instance)
   struct objlist *ChildObjList, *ChildListEnd;
   struct objlist *ChildStart, *ChildEnd, *ParentEnd, *ParentNext;
   struct nlist *ThisCell;
-  struct  nlist *ChildCell;
+  struct nlist *ChildCell;
   struct objlist *tmp, *ob2, *ob3;
-  int	notdone, rnodenum;
-  char	tmpstr[1024];
-  int	nextnode, oldmax, numflat = 0;
+  int	 notdone, rnodenum;
+  char	 tmpstr[1024];
+  int	 nextnode, oldmax, numflat = 0;
+  struct objlist *myObject_p, *myPort_p;
+  struct objlist *myFirstPin_p, *myPin_p;
+  int    myDeleteCount = 0;
 #if !OLDPREFIX
-  int     prefixlength;
+  int    prefixlength;
 #endif
 
   if (name == NULL) {
@@ -599,6 +602,38 @@ int flattenInstancesOf(char *name, int fnum, char *instance)
   }
   CacheNodeNames(ThisCell);
   ThisCell->dumped = 1;		/* indicate cell has been flattened */
+
+  // Remove disconnected ports.
+  // Fprintf(stdout, "DEBUG: check pins for %s of %d\n", name, fnum);
+
+  myFirstPin_p = NULL;
+
+  // Save first pin definition so we don't have to search for each port
+  for (myObject_p = ThisCell->cell; myObject_p != NULL; myObject_p = myObject_p->next) {
+    if (myObject_p->type >= FIRSTPIN) {
+      myFirstPin_p = myObject_p;
+      break;
+    }
+  }
+  if (myFirstPin_p != NULL) {  // Not a black box. Black boxes contain no pins.
+    // For each port, check for pin connection. If none, mark for deletion. 
+    // Assumes that all ports occur at the beginning of the list
+    for (myPort_p = ThisCell->cell; myPort_p != NULL && IsPort(myPort_p);
+		myPort_p = myPort_p->next ) {
+      for (myPin_p = myFirstPin_p; myPin_p != NULL; myPin_p = myPin_p->next) {
+        if (myPort_p->node == myPin_p->node) {  // only need to find one connection
+          break;
+        }
+      }
+      if (myPin_p == NULL) {  // mark disconnected ports
+        myDeleteCount++;
+        myPort_p->node = -2;
+      }
+    }
+    if (myDeleteCount > 0) {  // delete disconnected ports
+      CleanupPins(name, fnum);
+    }
+  }
   return numflat;
 }
 
@@ -1582,7 +1617,8 @@ PrematchLists(char *name1, int file1, char *name2, int file2)
 			}
 		    }
 		    else {
-		       match = 0;
+		       // Apply recursive flattening when a cell exists in
+		       // one circuit but not the other.
 		       break;
 		    }
 		}