diff --git a/Makefile b/Makefile
index 75b825a..289dff7 100644
--- a/Makefile
+++ b/Makefile
@@ -50,7 +50,7 @@ pkg/sdk/client/dist/client.js: tools/esbuild/bin/esbuild node_modules
 		pkg/sdk/client/src/index.ts \
 		--bundle \
 		--sourcemap \
-		--target=es2020 \
+		--target=es2015 \
 		--format=iife \
 		--global-name=Edge \
 		--define:global=window \