diff --git a/awx/api/serializers.py b/awx/api/serializers.py
index f198566c55..2f32657f29 100644
--- a/awx/api/serializers.py
+++ b/awx/api/serializers.py
@@ -1015,6 +1015,13 @@ class InventorySourceOptionsSerializer(BaseSerializer):
         # FIXME
         return attrs
 
+    def validate_source_script(self, attrs, source):
+        src = attrs.get(source, None)
+        if 'source' in attrs and attrs.get('source', '') == 'custom':
+            if src is None or src == '':
+                raise serializers.ValidationError("source_script must be provided")
+        return attrs
+
     def validate_source_vars(self, attrs, source):
         # source_env must be blank, a valid JSON or YAML dict, or ...
         # FIXME: support key=value pairs.