diff --git a/modules/camera/3_4/v4l2_camera.cpp b/modules/camera/3_4/v4l2_camera.cpp
index 3e5b859..2bc0c9f 100644
--- a/modules/camera/3_4/v4l2_camera.cpp
+++ b/modules/camera/3_4/v4l2_camera.cpp
@@ -295,32 +295,36 @@
 bool V4L2Camera::dequeueRequestBuffers() {
   // Dequeue a buffer.
   uint32_t result_index;
-  int res = device_->DequeueBuffer(&result_index);
-  if (res) {
-    if (res == -EAGAIN) {
-      // EAGAIN just means nothing to dequeue right now.
-      // Wait until something is available before looping again.
-      std::unique_lock<std::mutex> lock(in_flight_lock_);
-      while (in_flight_.empty()) {
-        buffers_in_flight_.wait(lock);
+  int res;
+
+  {
+    std::lock_guard<std::mutex> guard(in_flight_lock_);
+    res = device_->DequeueBuffer(&result_index);
+    if (!res) {
+      // Find the associated request and complete it.
+      auto index_request = in_flight_.find(result_index);
+      if (index_request != in_flight_.end()) {
+        completeRequest(index_request->second, 0);
+        in_flight_.erase(index_request);
+      } else {
+        HAL_LOGW(
+            "Dequeued non in-flight buffer index %d. "
+            "This buffer may have been flushed from the HAL but not the device.",
+            index_request->first);
       }
-    } else {
-      HAL_LOGW("Device failed to dequeue buffer: %d", res);
+      return true;
     }
-    return true;
   }
 
-  // Find the associated request and complete it.
-  std::lock_guard<std::mutex> guard(in_flight_lock_);
-  auto index_request = in_flight_.find(result_index);
-  if (index_request != in_flight_.end()) {
-    completeRequest(index_request->second, 0);
-    in_flight_.erase(index_request);
+  if (res == -EAGAIN) {
+    // EAGAIN just means nothing to dequeue right now.
+    // Wait until something is available before looping again.
+    std::unique_lock<std::mutex> lock(in_flight_lock_);
+    while (in_flight_.empty()) {
+      buffers_in_flight_.wait(lock);
+    }
   } else {
-    HAL_LOGW(
-        "Dequeued non in-flight buffer index %d. "
-        "This buffer may have been flushed from the HAL but not the device.",
-        index_request->first);
+    HAL_LOGW("Device failed to dequeue buffer: %d", res);
   }
   return true;
 }
diff --git a/modules/camera/3_4/v4l2_wrapper.cpp b/modules/camera/3_4/v4l2_wrapper.cpp
index 3fafffd..b5a1c71 100644
--- a/modules/camera/3_4/v4l2_wrapper.cpp
+++ b/modules/camera/3_4/v4l2_wrapper.cpp
@@ -535,6 +535,7 @@
     std::lock_guard<std::mutex> guard(buffer_queue_lock_);
     for (int i = 0; i < buffers_.size(); ++i) {
       if (!buffers_[i]) {
+        buffers_[i] = true;
         index = i;
         break;
       }
@@ -557,6 +558,9 @@
   // and fill out remaining fields.
   if (IoctlLocked(VIDIOC_QUERYBUF, &device_buffer) < 0) {
     HAL_LOGE("QUERYBUF fails: %s", strerror(errno));
+    // Return buffer index.
+    std::lock_guard<std::mutex> guard(buffer_queue_lock_);
+    buffers_[index] = false;
     return -ENODEV;
   }
 
@@ -565,18 +569,20 @@
       gralloc_->lock(camera_buffer, format_->bytes_per_line(), &device_buffer);
   if (res) {
     HAL_LOGE("Gralloc failed to lock buffer.");
+    // Return buffer index.
+    std::lock_guard<std::mutex> guard(buffer_queue_lock_);
+    buffers_[index] = false;
     return res;
   }
   if (IoctlLocked(VIDIOC_QBUF, &device_buffer) < 0) {
     HAL_LOGE("QBUF fails: %s", strerror(errno));
     gralloc_->unlock(&device_buffer);
+    // Return buffer index.
+    std::lock_guard<std::mutex> guard(buffer_queue_lock_);
+    buffers_[index] = false;
     return -ENODEV;
   }
 
-  // Mark the buffer as in flight.
-  std::lock_guard<std::mutex> guard(buffer_queue_lock_);
-  buffers_[index] = true;
-
   if (enqueued_index) {
     *enqueued_index = index;
   }