1 files changed, 14 insertions, 6 deletions

diff --git a/src/font.c b/src/font.c
index cc57af12141..dfc636e3313 100644
--- a/src/font.c
+++ b/src/font.c
@@ -241,17 +241,25 @@ font_intern_prop (const char *str, ptrdiff_t len, int force_symbol)
 
   if (len == 1 && *str == '*')
     return Qnil;
-  if (!force_symbol && len >=1 && isdigit (*str))
+  if (!force_symbol && 0 < len && '0' <= *str && *str <= '9')
     {
       for (i = 1; i < len; i++)
-        if (! isdigit (str[i]))
+        if (! ('0' <= str[i] && str[i] <= '9'))
           break;
       if (i == len)
         {
-          Lisp_Object num = string_to_number (str, 10, 0);
-          if (! INTEGERP (num))
-            xsignal1 (Qoverflow_error, num);
-          return num;
+          EMACS_INT n;
+
+          i = 0;
+          for (n = 0; (n += str[i++] - '0') <= MOST_POSITIVE_FIXNUM; n *= 10)
+            {
+              if (i == len)
+                return make_number (n);
+              if (MOST_POSITIVE_FIXNUM / 10 < n)
+                break;
+            }
+
+          xsignal1 (Qoverflow_error, make_string (str, len));
         }
     }