diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index fde397e8a..e06be6487 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -53,7 +53,7 @@ int qcow2_grow_l1_table(BlockDriverState *bs, int min_size, bool exact_size)
     }
 
 #ifdef DEBUG_ALLOC2
-    printf("grow l1_table from %d to %d\n", s->l1_size, new_l1_size);
+    fprintf(stderr, "grow l1_table from %d to %d\n", s->l1_size, new_l1_size);
 #endif
 
     new_l1_size2 = sizeof(uint64_t) * new_l1_size;
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index 2a915be57..fbf28dac1 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -422,7 +422,7 @@ static int QEMU_WARN_UNUSED_RESULT update_refcount(BlockDriverState *bs,
     int ret;
 
 #ifdef DEBUG_ALLOC2
-    printf("update_refcount: offset=%" PRId64 " size=%" PRId64 " addend=%d\n",
+    fprintf(stderr, "update_refcount: offset=%" PRId64 " size=%" PRId64 " addend=%d\n",
            offset, length, addend);
 #endif
     if (length < 0) {
@@ -556,7 +556,7 @@ retry:
         }
     }
 #ifdef DEBUG_ALLOC2
-    printf("alloc_clusters: size=%" PRId64 " -> %" PRId64 "\n",
+    fprintf(stderr, "alloc_clusters: size=%" PRId64 " -> %" PRId64 "\n",
             size,
             (s->free_cluster_index - nb_clusters) << s->cluster_bits);
 #endif