diff --git a/Shorewall/lib.core b/Shorewall/lib.core
index 5cc160d91..a8b5ea222 100644
--- a/Shorewall/lib.core
+++ b/Shorewall/lib.core
@@ -629,10 +629,12 @@ interface_is_usable() # $1 = interface
     local status;
     status=0
 
-    if [ "$1" != lo -a "$COMMAND" != enable ]; then
+    if [ "$1" != lo ]; then
 	if interface_is_up $1 && [ "$(find_first_interface_address_if_any $1)" != 0.0.0.0 ]; then
-	    run_isusable_exit $1
+	    [ "$COMMAND" = enable ] || run_isusable_exit $1
 	    status=$?
+	else
+	    status=1
 	fi
     fi
 
@@ -1028,10 +1030,12 @@ interface_is_usable() # $1 = interface
     local status;
     status=0
 
-    if [ "$1" != lo -a "$COMMAND" != enable ]; then
+    if [ "$1" != lo ]; then
 	if interface_is_up $1 && [ "$(find_first_interface_address_if_any $1)" != :: ]; then
-	    run_isusable_exit $1
+	    [ "$COMMAND" = enable ] || run_isusable_exit $1
 	    status=$?
+	else
+	    status=1
 	fi
     fi