diff --git a/test/unit/EthApiTest.php b/test/unit/EthApiTest.php
index 61f8ff6..ab2f32b 100644
--- a/test/unit/EthApiTest.php
+++ b/test/unit/EthApiTest.php
@@ -687,7 +687,7 @@ class EthApiTest extends TestCase
                 // infura banned us to uninstall filter
                 return $this->assertTrue($err !== null);
             }
-            $this->assertTrue(is_string($filter));
+            $this->assertTrue(is_bool($filter));
         });
     }