--- a/test/eventsource.h
+++ b/test/eventsource.h
@@ -24,6 +24,9 @@
 #include <rapidjson/document.h>
 #include <vector>
 
+// Definition needed for musl
+typedef unsigned long ulong;
+
 class EventSource {
 public:
     EventSource(kj::AsyncIoContext& ctx, const char* httpConnectAddr, const char* path) :