diff --git a/CHANGELOG.md b/CHANGELOG.md
index bf43a1ea..2acbca9c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Changelog
 
+## Unreleased
+
+- Reverted behavioral change to `sanitize_key_part()`
+
 ## 2.5.1
 
 - Added timeouts to diagnostics
diff --git a/includes/object-cache.php b/includes/object-cache.php
index e91a18e1..9ad8a0c1 100644
--- a/includes/object-cache.php
+++ b/includes/object-cache.php
@@ -2539,7 +2539,7 @@ public function fast_build_key( $key, $group = 'default' ) {
      * @return string        Sanitized string.
      */
     protected function sanitize_key_part( $part ) {
-        return str_replace( ':', '-', is_scalar( $part ) ? (string) $part : '' );
+        return is_string( $part ) ? str_replace( ':', '-', $part ) : $part;
     }
 
     /**