diff --git a/src/charset.c b/src/charset.c
index e11a8366d5..a5a5a944dc 100644
--- a/src/charset.c
+++ b/src/charset.c
@@ -1870,8 +1870,7 @@ although this usage is obsolescent.  */)
 
 DEFUN ("encode-char", Fencode_char, Sencode_char, 2, 2, 0,
        doc: /* Encode the character CH into a code-point of CHARSET.
-Return the encoded code-point, a fixnum if its value is small enough,
-otherwise a bignum.
+Return the encoded code-point, a fixnum.
 Return nil if CHARSET doesn't support CH.  */)
   (Lisp_Object ch, Lisp_Object charset)
 {
@@ -1886,7 +1885,8 @@ Return nil if CHARSET doesn't support CH.  */)
   code = ENCODE_CHAR (charsetp, c);
   if (code == CHARSET_INVALID_CODE (charsetp))
     return Qnil;
-  return INT_TO_INTEGER (code);
+  eassert (!FIXNUM_OVERFLOW_P (code));
+  return make_fixnum (code);
 }