diff --git a/rules/CodingStyle/ClassNameImport/ClassNameImportSkipVoter/ClassLikeNameClassNameImportSkipVoter.php b/rules/CodingStyle/ClassNameImport/ClassNameImportSkipVoter/ClassLikeNameClassNameImportSkipVoter.php
index fb522f0ecbd..035fda21883 100644
--- a/rules/CodingStyle/ClassNameImport/ClassNameImportSkipVoter/ClassLikeNameClassNameImportSkipVoter.php
+++ b/rules/CodingStyle/ClassNameImport/ClassNameImportSkipVoter/ClassLikeNameClassNameImportSkipVoter.php
@@ -47,7 +47,7 @@ public function shouldSkip(File $file, FullyQualifiedObjectType $fullyQualifiedO
 
         $shortNameLowered = $fullyQualifiedObjectType->getShortNameLowered();
         $fullyQualifiedObjectTypeNamespace = strtolower(
-            substr($fullyQualifiedObjectType->getClassName(), 0, -strlen($fullyQualifiedObjectType->getShortName()) - 1)
+            substr($fullyQualifiedObjectType->getClassName(), 0, -strlen($fullyQualifiedObjectType->getShortName()) - 1) ?: ''
         );
 
         foreach ($classLikeNames as $classLikeName) {