diff --git a/heartbeat/Filesystem b/heartbeat/Filesystem
index 05a0ad7..35bf20d 100755
--- a/heartbeat/Filesystem
+++ b/heartbeat/Filesystem
@@ -844,6 +844,12 @@ Filesystem_monitor_10()
 #
 Filesystem_monitor_20()
 {
+	if [ "$blockdevice" = "no" ] ; then
+		if [ "$FSTYPE" = "cifs" ] || [ "$FSTYPE" = "smbfs" ]; then
+			# O_DIRECT not supported
+			dd_opts="oflag=sync bs=512 conv=fsync,sync"
+		fi
+    fi
 	# Writing to the device in O_DIRECT mode is imperative
 	# to bypass caches.
 	dd_opts="oflag=direct,sync bs=512 conv=fsync,sync"