diff --git a/thread_pthread.c b/thread_pthread.c
index 20d0b598cf..78c66a0c63 100644
--- a/thread_pthread.c
+++ b/thread_pthread.c
@@ -73,8 +73,7 @@ gvl_acquire_common(rb_vm_t *vm)
 {
     if (vm->gvl.acquired) {
 
-	vm->gvl.waiting++;
-	if (vm->gvl.waiting == 1) {
+	if (!vm->gvl.waiting++) {
 	    /*
 	     * Wake up timer thread iff timer thread is slept.
 	     * When timer thread is polling mode, we don't want to
@@ -87,7 +86,7 @@ gvl_acquire_common(rb_vm_t *vm)
             rb_native_cond_wait(&vm->gvl.cond, &vm->gvl.lock);
 	}
 
-	vm->gvl.waiting--;
+	--vm->gvl.waiting;
 
 	if (vm->gvl.need_yield) {
 	    vm->gvl.need_yield = 0;