diff --git a/.changeset/perfect-wasps-rhyme.md b/.changeset/perfect-wasps-rhyme.md
new file mode 100644
index 00000000..ae9c359c
--- /dev/null
+++ b/.changeset/perfect-wasps-rhyme.md
@@ -0,0 +1,5 @@
+---
+"microbundle": patch
+---
+
+fix default extension to cjs for package.json "type":"module"