diff --git a/strings/ctype-sjis.c b/strings/ctype-sjis.c
index 0cb30a9b6ee..20f0081888f 100644
--- a/strings/ctype-sjis.c
+++ b/strings/ctype-sjis.c
@@ -4576,12 +4576,7 @@ uint my_well_formed_len_sjis(CHARSET_INFO *cs __attribute__((unused)),
   const char *b0= b;
   while (pos && b < e)
   {
-    /*
-      Cast to int8 for extra safety.
-      "char" can be unsigned by default
-      on some platforms.
-    */
-    if (((int8)b[0]) >= 0)
+    if ((uchar) b[0] < 128)
     {
       /* Single byte ascii character */
       b++;
diff --git a/strings/ctype-utf8.c b/strings/ctype-utf8.c
index 4d2bff5e89f..83725878a50 100644
--- a/strings/ctype-utf8.c
+++ b/strings/ctype-utf8.c
@@ -2129,12 +2129,7 @@ int my_strcasecmp_utf8(CHARSET_INFO *cs, const char *s, const char *t)
   {
     my_wc_t s_wc,t_wc;
     
-    /*
-      Cast to int8 for extra safety.
-      char can be unsigned by default
-      on some platforms.
-    */
-    if (((int8)s[0]) >= 0)
+    if ((uchar) s[0] < 128)
     {
       /* 
         s[0] is between 0 and 127.
@@ -2181,7 +2176,7 @@ int my_strcasecmp_utf8(CHARSET_INFO *cs, const char *s, const char *t)
     
     /* Do the same for the second string */
     
-    if (((int8)t[0]) >= 0)
+    if ((uchar) t[0] < 128)
     {
       /* Convert single byte character into weight */
       t_wc= plane00[(uchar) t[0]].tolower;