diff --git a/src/mbyte.c b/src/mbyte.c
index 085b0ea..846ce98 100644
--- a/src/mbyte.c
+++ b/src/mbyte.c
@@ -667,7 +667,7 @@
 	     * API */
 	    n = IsDBCSLeadByteEx(enc_dbcs, (BYTE)i) ? 2 : 1;
 #else
-# ifdef MACOS
+# if defined(MACOS) || defined(__amigaos4__)
 	    /*
 	     * if mblen() is not available, character which MSB is turned on
 	     * are treated as leading byte character. (note : This assumption