diff --git a/stlinkv3_spi.c b/stlinkv3_spi.c
index d56f305..ae865be 100644
--- a/stlinkv3_spi.c
+++ b/stlinkv3_spi.c
@@ -496,6 +496,7 @@
 				 speed_str);
 			msg_perr("Please pass the parameter "
 				 "with a simple non-zero number in kHz\n");
+			free(speed_str);
 			return -1;
 		}
 		free(speed_str);