diff --git a/src/Executor/ReferenceExecutor.php b/src/Executor/ReferenceExecutor.php
index 001dbd5..6e35f7c 100644
--- a/src/Executor/ReferenceExecutor.php
+++ b/src/Executor/ReferenceExecutor.php
@@ -259,9 +259,11 @@ class ReferenceExecutor implements ExecutorImplementation
                 return $result->then(
                     null,
                     function ($error) {
-                        $this->exeContext->addError($error);
+                        if ($error instanceof Error) {
+                            $this->exeContext->addError($error);
 
-                        return $this->exeContext->promises->createFulfilled(null);
+                            return $this->exeContext->promises->createFulfilled(null);
+                        }
                     }
                 );
             }
diff --git a/src/Type/SchemaValidationContext.php b/src/Type/SchemaValidationContext.php
index f00d3e5..5e52164 100644
--- a/src/Type/SchemaValidationContext.php
+++ b/src/Type/SchemaValidationContext.php
@@ -252,7 +252,7 @@ class SchemaValidationContext
             if (! $type instanceof NamedType) {
                 $this->reportError(
                     'Expected GraphQL named type but got: ' . Utils::printSafe($type) . '.',
-                    is_object($type) ? $type->astNode : null
+                    $type instanceof Type ? $type->astNode : null
                 );
                 continue;
             }