diff --git a/eventrouter/internal/os_types.h b/eventrouter/internal/os_types.h
index 40b80c7..fac7f08 100644
--- a/eventrouter/internal/os_types.h
+++ b/eventrouter/internal/os_types.h
@@ -19,7 +19,7 @@
 #elif ER_IMPLEMENTATION == ER_IMPL_POSIX
 #include <pthread.h>
 #define ErTaskHandle_t pthread_t
-#elif
+#else
 #error "Unexpected value in ER_IMPLEMENTATION"
 #endif