diff --git a/server/FirewallController.cpp b/server/FirewallController.cpp
index 0746316..17c6da4 100644
--- a/server/FirewallController.cpp
+++ b/server/FirewallController.cpp
@@ -69,6 +69,11 @@
 }
 
 int FirewallController::setInterfaceRule(const char* iface, FirewallRule rule) {
+    if (!isIfaceName(iface)) {
+        errno = ENOENT;
+        return -1;
+    }
+
     const char* op;
     if (rule == ALLOW) {
         op = "-I";