diff --git a/src/core/ngx_shmtx.c b/src/core/ngx_shmtx.c
index a62999f..6230dc0 100644
--- a/src/core/ngx_shmtx.c
+++ b/src/core/ngx_shmtx.c
@@ -101,6 +101,7 @@
             (void) ngx_atomic_fetch_add(mtx->wait, 1);
 
             if (*mtx->lock == 0 && ngx_atomic_cmp_set(mtx->lock, 0, ngx_pid)) {
+                (void) ngx_atomic_fetch_add(mtx->wait, -1);
                 return;
             }
 
@@ -174,7 +175,7 @@
 
         wait = *mtx->wait;
 
-        if (wait == 0) {
+        if ((ngx_atomic_int_t) wait <= 0) {
             return;
         }