diff --git a/include/block/aio-wait.h b/include/block/aio-wait.h
index 783d3678dd..c85a62f798 100644
--- a/include/block/aio-wait.h
+++ b/include/block/aio-wait.h
@@ -57,7 +57,8 @@ typedef struct {
 /**
  * AIO_WAIT_WHILE:
  * @wait: the aio wait object
- * @ctx: the aio context
+ * @ctx: the aio context, or NULL if multiple aio contexts (for which the
+ *       caller does not hold a lock) are involved in the polling condition.
  * @cond: wait while this conditional expression is true
  *
  * Wait while a condition is true.  Use this to implement synchronous
@@ -75,7 +76,7 @@ typedef struct {
     bool waited_ = false;                                          \
     AioWait *wait_ = (wait);                                       \
     AioContext *ctx_ = (ctx);                                      \
-    if (in_aio_context_home_thread(ctx_)) {                        \
+    if (ctx_ && in_aio_context_home_thread(ctx_)) {                \
         while ((cond)) {                                           \
             aio_poll(ctx_, true);                                  \
             waited_ = true;                                        \
@@ -86,9 +87,13 @@ typedef struct {
         /* Increment wait_->num_waiters before evaluating cond. */ \
         atomic_inc(&wait_->num_waiters);                           \
         while ((cond)) {                                           \
-            aio_context_release(ctx_);                             \
+            if (ctx_) {                                            \
+                aio_context_release(ctx_);                         \
+            }                                                      \
             aio_poll(qemu_get_aio_context(), true);                \
-            aio_context_acquire(ctx_);                             \
+            if (ctx_) {                                            \
+                aio_context_acquire(ctx_);                         \
+            }                                                      \
             waited_ = true;                                        \
         }                                                          \
         atomic_dec(&wait_->num_waiters);                           \