diff --git a/block.c b/block.c
index 9c106a8..1919d19 100644
--- a/block.c
+++ b/block.c
@@ -1691,6 +1691,10 @@
             merge = bs->drv->bdrv_merge_requests(bs, &reqs[outidx], &reqs[i]);
         }
 
+        if (reqs[outidx].qiov->niov + reqs[i].qiov->niov + 1 > IOV_MAX) {
+            merge = 0;
+        }
+
         if (merge) {
             size_t size;
             QEMUIOVector *qiov = qemu_mallocz(sizeof(*qiov));
diff --git a/qemu-common.h b/qemu-common.h
index ae4f23b..b09f717 100644
--- a/qemu-common.h
+++ b/qemu-common.h
@@ -54,6 +54,10 @@
     void *iov_base;
     size_t iov_len;
 };
+/*
+ * Use the same value as Linux for now.
+ */
+#define IOV_MAX		1024
 #else
 #include <sys/uio.h>
 #endif