diff --git a/signal.c b/signal.c
index f0513381..743c9f32 100644
--- a/signal.c
+++ b/signal.c
@@ -793,9 +793,9 @@ parse_sigset_t (const char *str, sigset_t *set)
 		if (*p >= '0' && *p <= '9')
 			digit = *p - '0';
 		else if (*p >= 'a' && *p <= 'f')
-			digit = *p - 'a';
+			digit = *p - 'a' + 10;
 		else if (*p >= 'A' && *p <= 'F')
-			digit = *p - 'A';
+			digit = *p - 'A' + 10;
 		else
 			break;
 		if (digit & 1)