diff --git a/rtl/wasi/systhrd.inc b/rtl/wasi/systhrd.inc
index b81b07c2fa..bbaa09822a 100644
--- a/rtl/wasi/systhrd.inc
+++ b/rtl/wasi/systhrd.inc
@@ -20,7 +20,7 @@
 {$endif FPC_WASM_THREADS}
 
 {$DEFINE FPC_WASM_MAIN_THREAD_CAN_WAIT}
-{$UNDEF FPC_WASM_WORKER_THREADS_CAN_WAIT}
+{$DEFINE FPC_WASM_WORKER_THREADS_CAN_WAIT}
 
 {//$DEFINE DEBUGWASMTHREADS}