diff --git a/src/jtag3.c b/src/jtag3.c
index 36aed4f0..bab35032 100644
--- a/src/jtag3.c
+++ b/src/jtag3.c
@@ -1569,7 +1569,7 @@ int jtag3_open_common(PROGRAMMER *pgm, const char *port) {
     pmsg_notice("found CMSIS-DAP compliant device, using EDBG protocol\n");
   }
 
-  // Get USB serial number
+  // Get USB serial number function if function pointer is present
   if (serial_serno)
     pgm->usbsn = serial_serno();
 
diff --git a/src/stk500v2.c b/src/stk500v2.c
index 095b3248..beecf4c1 100644
--- a/src/stk500v2.c
+++ b/src/stk500v2.c
@@ -1578,7 +1578,7 @@ static int stk500v2_open(PROGRAMMER *pgm, const char *port) {
     return -1;
   }
 
-  // Get USB serial number
+  // Get USB serial number function if function pointer is present
   if (serial_serno)
     pgm->usbsn = serial_serno();