diff --git a/.changeset/chilled-paws-confess.md b/.changeset/chilled-paws-confess.md
new file mode 100644
index 00000000..2824711d
--- /dev/null
+++ b/.changeset/chilled-paws-confess.md
@@ -0,0 +1,5 @@
+---
+"microbundle": patch
+---
+
+Support [extending a UMD global](https://rollupjs.org/guide/en/#outputextend) by prefixing the package.json `"amdName"` field (eg: `"global.xyz"`).
diff --git a/src/index.js b/src/index.js
index 87a9601f..7e1a8ee2 100644
--- a/src/index.js
+++ b/src/index.js
@@ -590,7 +590,8 @@ function createConfig(options, entry, format, writeMeta) {
 				return shebang[options.name];
 			},
 			format: modern ? 'es' : format,
-			name: options.name,
+			name: options.name && options.name.replace(/^global\./, ''),
+			extend: /^global\./.test(options.name),
 			dir: outputDir,
 			entryFileNames: outputEntryFileName,
 		},