diff --git a/ui/opensnitch/dialogs/firewall_rule.py b/ui/opensnitch/dialogs/firewall_rule.py
index 9e8eca06..4e5bc3fa 100644
--- a/ui/opensnitch/dialogs/firewall_rule.py
+++ b/ui/opensnitch/dialogs/firewall_rule.py
@@ -1445,10 +1445,10 @@ The value must be in the format: VALUE/UNITS/TIME, for example:
                         # 3. otherwise validate that the entered value is an
                         # int
                         try:
-                            if "," in statem_value or "-" in statem_value:
-                                raise ValueError("port entered is multiport or a port range")
                             service_idx = self.net_srv.service_by_name(statem_value)
                             statem_value = self.net_srv.port_by_index(service_idx)
+                            if service_idx > 0 and "," in statem_value or "-" in statem_value:
+                                raise ValueError("port entered is multiport or a port range")
                         except:
                             if "," not in statem_value and "-" not in statem_value:
                                 if not self._is_valid_int_value(statem_value):
diff --git a/ui/opensnitch/utils/__init__.py b/ui/opensnitch/utils/__init__.py
index e7f73ad6..03793949 100644
--- a/ui/opensnitch/utils/__init__.py
+++ b/ui/opensnitch/utils/__init__.py
@@ -435,16 +435,28 @@ class NetworkServices():
         return self.srv_array
 
     def service_by_index(self, idx):
-        return self.srv_array[idx]
+        try:
+            return self.srv_array[idx]
+        except:
+            return ""
 
     def service_by_name(self, name):
-        return self.srv_array.index(name)
+        try:
+            return self.srv_array.index(name)
+        except:
+            return -1
 
     def port_by_index(self, idx):
-        return self.ports_list[idx]
+        try:
+            return self.ports_list[idx]
+        except:
+            return -1
 
     def index_by_port(self, port):
-        return self.ports_list.index(str(port))
+        try:
+            return self.ports_list.index(str(port))
+        except:
+            return -1
 
 class Icons():
     """Util to display Qt's built-in icons when the system is not configured as