diff --git a/tools/spi/spidev_test.c b/tools/spi/spidev_test.c
index 8a73d8185316..f3825b676e38 100644
--- a/tools/spi/spidev_test.c
+++ b/tools/spi/spidev_test.c
@@ -284,7 +284,7 @@ static void parse_opts(int argc, char *argv[])
 
 static void transfer_escaped_string(int fd, char *str)
 {
-	size_t size = strlen(str + 1);
+	size_t size = strlen(str);
 	uint8_t *tx;
 	uint8_t *rx;