diff --git a/modules/module-lua-scripting/api.c b/modules/module-lua-scripting/api.c
index f35785d8..bad41b19 100644
--- a/modules/module-lua-scripting/api.c
+++ b/modules/module-lua-scripting/api.c
@@ -511,6 +511,7 @@ object_interest_new_add_constraint (lua_State *L, GType type,
 
   switch (verb) {
   case WP_CONSTRAINT_VERB_EQUALS:
+  case WP_CONSTRAINT_VERB_NOT_EQUALS:
   case WP_CONSTRAINT_VERB_MATCHES: {
     lua_geti (L, constraint_idx, 3);
     value = constraint_value_to_variant (L, -1);
diff --git a/modules/module-lua-scripting/api.lua b/modules/module-lua-scripting/api.lua
index 6400402a..cbab5573 100644
--- a/modules/module-lua-scripting/api.lua
+++ b/modules/module-lua-scripting/api.lua
@@ -53,7 +53,7 @@ local function Constraint (spec)
   end
 
   -- check if we got the right amount of values
-  if verb == "=" or verb == "#" then
+  if verb == "=" or verb == "!" or verb == "#" then
     assert (spec[3] ~= nil,
       "Constraint: " .. verbs[verb] .. ": expected constraint value")
   elseif verb == "c" then