diff --git a/apps/px4/tests/test_sensors.c b/apps/px4/tests/test_sensors.c
index c7bcc89287..01fa48cc9d 100644
--- a/apps/px4/tests/test_sensors.c
+++ b/apps/px4/tests/test_sensors.c
@@ -435,7 +435,7 @@ hmc5883l(int argc, char *argv[])
 	fflush(stdout);
 
 	int		fd;
-	int16_t	buf[3] = {0, 0, 0};
+	int16_t	buf[7] = {0, 0, 0};
 	int		ret;
 
 	fd = open("/dev/hmc5883l", O_RDONLY);