diff --git a/kernel/trunk/fs/ext.inc b/kernel/trunk/fs/ext.inc
index 0cffa353bb..61aa52c9f8 100644
--- a/kernel/trunk/fs/ext.inc
+++ b/kernel/trunk/fs/ext.inc
@@ -586,6 +586,7 @@ extfsExtentAlloc:
         or      eax, -1
         rep stosd
         mov     ecx, ebx
+        jecxz   .done
         neg     ecx
         add     ecx, 32
         shr     eax, cl