diff --git a/src/Plugin/RulesAction/EntityCreateDeriver.php b/src/Plugin/RulesAction/EntityCreateDeriver.php
index aa096ae..b6acea0 100644
--- a/src/Plugin/RulesAction/EntityCreateDeriver.php
+++ b/src/Plugin/RulesAction/EntityCreateDeriver.php
@@ -89,7 +89,19 @@ class EntityCreateDeriver extends DeriverBase implements ContainerDeriverInterfa
         }
 
         $item_definition = $definition->getItemDefinition();
-        $type_definition = $item_definition->getPropertyDefinition($item_definition->getMainPropertyName());
+
+        $main_property_name = $item_definition->getMainPropertyName();
+
+        if (is_null($main_property_name)) {
+          continue;
+        }
+
+        $type_definition = $item_definition->getPropertyDefinition($main_property_name);
+
+        // Get around types which don't properly define their main property (or lack of one)
+        if (is_null($type_definition)) {
+          continue;
+        }
 
         // If this is an entity reference then we expect the target type as
         // context.