diff --git a/configs/nucleus2g/README.txt b/configs/nucleus2g/README.txt
index 21b04a08fbf..4d88654c5d7 100755
--- a/configs/nucleus2g/README.txt
+++ b/configs/nucleus2g/README.txt
@@ -443,7 +443,9 @@ Nucleus 2G Configuration Options
     CONFIG_USBHOST_TDBUFSIZE
       Size of one transfer descriptor buffer
     CONFIG_USBHOST_IOBUFSIZE
-      Size of one end-user I/O buffer
+      Size of one end-user I/O buffer.  This can be zero if the
+      application can guarantee that all end-user I/O buffers
+      reside in AHB SRAM.
 
 USB Host Configuration
 ^^^^^^^^^^^^^^^^^^^^^^
diff --git a/configs/olimex-lpc1766stk/README.txt b/configs/olimex-lpc1766stk/README.txt
index cd7a1ca4936..eae9685eaa7 100755
--- a/configs/olimex-lpc1766stk/README.txt
+++ b/configs/olimex-lpc1766stk/README.txt
@@ -689,7 +689,9 @@ Olimex LPC1766-STK Configuration Options
     CONFIG_USBHOST_TDBUFSIZE
       Size of one transfer descriptor buffer
     CONFIG_USBHOST_IOBUFSIZE
-      Size of one end-user I/O buffer
+      Size of one end-user I/O buffer.  This can be zero if the
+      application can guarantee that all end-user I/O buffers
+      reside in AHB SRAM.
 
 USB Host Configuration
 ^^^^^^^^^^^^^^^^^^^^^^