diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 0648291..6fe2c84 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -2347,7 +2347,7 @@
 			break;
 
 		base = 10;
-		is_sign = 0;
+		is_sign = false;
 
 		switch (*fmt++) {
 		case 'c':
@@ -2386,7 +2386,7 @@
 		case 'i':
 			base = 0;
 		case 'd':
-			is_sign = 1;
+			is_sign = true;
 		case 'u':
 			break;
 		case '%':