diff --git a/cores/arduino/USB/USBDesc.h b/cores/arduino/USB/USBDesc.h
index e4335aa911655ddf4e15760d155519867d7189ae..6088ee089fc80fdeee947e80a0d4a56746befafc 100644
--- a/cores/arduino/USB/USBDesc.h
+++ b/cores/arduino/USB/USBDesc.h
@@ -41,7 +41,7 @@
 #define CDC_TX CDC_ENDPOINT_IN
 #endif
 
-#define ISERIAL_MAX_LEN        20
+#define ISERIAL_MAX_LEN        33
 
 // Defined string description
 #define IMANUFACTURER	1