diff --git a/src/SignatureHelpProvider.php b/src/SignatureHelpProvider.php
index 04b272b..ed9522a 100644
--- a/src/SignatureHelpProvider.php
+++ b/src/SignatureHelpProvider.php
@@ -234,7 +234,7 @@ class SignatureHelpProvider
                 ++$i;
             }
         }
-        if (is_null($found)) {
+        if ($found === null) {
             $found = $i;
         }
         return $found;