diff --git a/daemon/usb.cpp b/daemon/usb.cpp
index 8c33ca5..3b29ab5 100644
--- a/daemon/usb.cpp
+++ b/daemon/usb.cpp
@@ -57,11 +57,12 @@
 // We can't find out whether we have support for AIO on ffs endpoints until we submit a read.
 static std::optional<bool> gFfsAioSupported;
 
+// Not all USB controllers support operations larger than 16k, so don't go above that.
 static constexpr size_t kUsbReadQueueDepth = 32;
-static constexpr size_t kUsbReadSize = 8 * PAGE_SIZE;
+static constexpr size_t kUsbReadSize = 4 * PAGE_SIZE;
 
 static constexpr size_t kUsbWriteQueueDepth = 32;
-static constexpr size_t kUsbWriteSize = 8 * PAGE_SIZE;
+static constexpr size_t kUsbWriteSize = 4 * PAGE_SIZE;
 
 static const char* to_string(enum usb_functionfs_event_type type) {
     switch (type) {