diff --git a/src/core/ngx_slab.c b/src/core/ngx_slab.c
index 57f2bff..b09d2e4 100644
--- a/src/core/ngx_slab.c
+++ b/src/core/ngx_slab.c
@@ -171,7 +171,7 @@
     if (size >= ngx_slab_max_size) {
 
         ngx_log_debug1(NGX_LOG_DEBUG_ALLOC, ngx_cycle->log, 0,
-                      "slab alloc: %uz", size);
+                       "slab alloc: %uz", size);
 
         page = ngx_slab_alloc_pages(pool, (size + ngx_pagesize - 1)
                                           >> ngx_pagesize_shift);