diff --git a/sys/src/libmp/port/strtomp.c b/sys/src/libmp/port/strtomp.c
index 17954fd04..78c38fe86 100644
--- a/sys/src/libmp/port/strtomp.c
+++ b/sys/src/libmp/port/strtomp.c
@@ -88,7 +88,7 @@ from8(char *a, mpint *b)
 	next = p;
 
 	i = 0;
-	x = 0;
+	x = y = 0;
 	while(p > a){
 		y = tab.t10[*(uchar*)--p];
 		x |= y << i;