diff --git a/classes/Tools/Storage/StorageContentHooks.php b/classes/Tools/Storage/StorageContentHooks.php
index 0ae729f7..e7819e82 100644
--- a/classes/Tools/Storage/StorageContentHooks.php
+++ b/classes/Tools/Storage/StorageContentHooks.php
@@ -191,11 +191,11 @@ private function processCoverBlock($id, $block_content) {
 					continue;
 				}
 
-				if (strpos($class[1], 'wp-block-cover') === false) {
+				if ( !preg_match("/wp-block-cover(\s|$)/ui", $class[1]) ) {
 					continue;
 				}
 
-				$block_content = str_replace($class[1], "{$class[1]} mcloud-attachment-{$id}", $block_content);
+				$block_content = preg_replace("/([\s'\"])({$class[1]})([\s'\"])/ui", "$1$2 mcloud-attachment-{$id} $3", $block_content);
 			}
 		}
 
@@ -1223,4 +1223,4 @@ public function calculateSrcSet($sources, $size_array, $image_src, $image_meta,
 		return $newSources;
 	}
 	//endregion
-}
\ No newline at end of file
+}