diff --git a/src/rtl_power.c b/src/rtl_power.c
index df3ceb7..86b24b4 100644
--- a/src/rtl_power.c
+++ b/src/rtl_power.c
@@ -133,7 +133,7 @@ void usage(void)
 		"\t[-d device_index (default: 0)]\n"
 		"\t[-g tuner_gain (default: automatic)]\n"
 		"\t[-p ppm_error (default: 0)]\n"
-		"\t[-T enable bias-T on GPIO PIN 0 (works for rtl-sdr.com v3 dongles)]\n"
+		"\t[-T enable bias-T on GPIO PIN 0 (works for rtl-sdr.com v3/v4 dongles)]\n"
 		"\tfilename (a '-' dumps samples to stdout)\n"
 		"\t (omitting the filename also uses stdout)\n"
 		"\n"