diff --git a/.changeset/quick-cows-chew.md b/.changeset/quick-cows-chew.md
new file mode 100644
index 0000000000..f06fba27b0
--- /dev/null
+++ b/.changeset/quick-cows-chew.md
@@ -0,0 +1,5 @@
+---
+'rrweb-snapshot': patch
+---
+
+allow passing null to maskTextClass/blockClass
diff --git a/packages/rrweb-snapshot/src/snapshot.ts b/packages/rrweb-snapshot/src/snapshot.ts
index 0201b9c647..7ee57be131 100644
--- a/packages/rrweb-snapshot/src/snapshot.ts
+++ b/packages/rrweb-snapshot/src/snapshot.ts
@@ -268,7 +268,7 @@ export function _isBlockedElement(
       if (element.classList.contains(blockClass)) {
         return true;
       }
-    } else {
+    } else if (blockClass) {
       for (let eIndex = element.classList.length; eIndex--; ) {
         const className = element.classList[eIndex];
         if (blockClass.test(className)) {
@@ -292,6 +292,7 @@ export function classMatchesRegex(
   checkAncestors: boolean,
 ): boolean {
   if (!node) return false;
+  if (!regex) return false;
   if (node.nodeType !== node.ELEMENT_NODE) {
     if (!checkAncestors) return false;
     return classMatchesRegex(node.parentNode, regex, checkAncestors);