1 files changed, 1 insertions, 1 deletions
diff --git a/rational.c b/rational.c
index f54cb70e24..13487363fb 100644
--- a/rational.c
+++ b/rational.c
@@ -1371,7 +1371,7 @@ string_to_r_internal(VALUE self)
 	    VALUE l;
 
 	    while (*p) {
-		if (isdigit(*p))
+		if (rb_isdigit(*p))
 		    count++;
 		p++;
 	    }