--- a/security/sandbox/linux/broker/SandboxBroker.cpp
+++ b/security/sandbox/linux/broker/SandboxBroker.cpp
@@ -879,17 +879,21 @@ SandboxBroker::ThreadMain(void)
         break;
       }
     } else {
       MOZ_ASSERT(perms == 0);
       AuditDenial(req.mOp, req.mFlags, perms, pathBuf);
     }
 
     const size_t numIO = ios[1].iov_len > 0 ? 2 : 1;
-    DebugOnly<const ssize_t> sent = SendWithFd(respfd, ios, numIO, openedFd);
+    const ssize_t sent = SendWithFd(respfd, ios, numIO, openedFd);
+    if (sent < 0) {
+      SANDBOX_LOG_ERROR("failed to send broker response to pid %d: %s", mChildPid,
+                        strerror(errno));
+    }
     close(respfd);
     MOZ_ASSERT(sent < 0 ||
                static_cast<size_t>(sent) == ios[0].iov_len + ios[1].iov_len);
 
     if (openedFd >= 0) {
       close(openedFd);
     }
   }