diff --git a/src/dos/drive_iso.cpp b/src/dos/drive_iso.cpp
index c3451001..4135d734 100644
--- a/src/dos/drive_iso.cpp
+++ b/src/dos/drive_iso.cpp
@@ -16,7 +16,7 @@
  *  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  */
 
-/* $Id: drive_iso.cpp,v 1.26 2009-06-19 18:28:10 c2woody Exp $ */
+/* $Id: drive_iso.cpp,v 1.27 2009-09-22 21:48:08 c2woody Exp $ */
 
 #include <cctype>
 #include <cstring>
@@ -430,7 +430,11 @@ void isoDrive::FreeDirIterator(const int dirIterator) {
 	
 	// if this was the last aquired iterator decrement nextFreeIterator
 	if ((dirIterator + 1) % MAX_OPENDIRS == nextFreeDirIterator) {
-		nextFreeDirIterator--;
+		if (nextFreeDirIterator>0) {
+			nextFreeDirIterator--;
+		} else {
+			nextFreeDirIterator = MAX_OPENDIRS-1;
+		}
 	}
 }