diff --git a/ch341funcs.c b/ch341funcs.c
index 3bed06b..55ba7cf 100644
--- a/ch341funcs.c
+++ b/ch341funcs.c
@@ -30,7 +30,7 @@ extern FILE *debugout, *verbout;
 uint32_t getnextpkt;                            // set by the callback function
 uint32_t syncackpkt;                            // synch / ack flag used by BULK OUT cb function
 uint16_t byteoffset;
-uint8_t *readbuf;
+extern uint8_t *readbuf;
 
 // --------------------------------------------------------------------------
 // ch341configure()
