diff --git a/src/etc/rc.d/netflow b/src/etc/rc.d/netflow
index fb6cbd2b4..5b73c5451 100755
--- a/src/etc/rc.d/netflow
+++ b/src/etc/rc.d/netflow
@@ -91,8 +91,9 @@ netflow_setup_interface()
         conf="11"
         echo "setup $interface"
     fi;
-    # avoid dots [.] in interface names to avoid issues with ngctl
-    interface=`echo $interface | sed 's/\./_/g'`
+
+    # prevent using special netgraph characters in interface names
+    interface=$(echo $interface | sed 's/[.:]/_/g')
 
     # remove earlier setup (if any)
     /usr/sbin/ngctl shutdown netflow_$interface: >/dev/null 2>&1