diff --git a/src/intl/charsets.c b/src/intl/charsets.c
index d08c575d..6df8e8ad 100644
--- a/src/intl/charsets.c
+++ b/src/intl/charsets.c
@@ -813,8 +813,9 @@ free_utf_table(void)
 {
 	int i;
 
+	/* Cast away const.  */
 	for (i = 128; i < 256; i++)
-		mem_free(utf_table[i].u.str);
+		mem_free((unsigned char *) utf_table[i].u.str);
 }
 
 static struct conv_table *
@@ -1191,7 +1192,7 @@ convert_string(struct conv_table *convert_table,
 	/* Iterate ;-) */
 
 	while (charspos < charslen) {
-		unsigned char *translit;
+		const unsigned char *translit;
 
 #define PUTC do { \
 		buffer[bufferpos++] = chars[charspos++]; \
diff --git a/src/intl/charsets.h b/src/intl/charsets.h
index 43259de0..edae15f6 100644
--- a/src/intl/charsets.h
+++ b/src/intl/charsets.h
@@ -44,7 +44,7 @@ struct conv_table {
 		 * However, if the translation table is to UTF-8,
 		 * then the strings in elements 0x80 to 0xFF are
 		 * allocated with mem_alloc.  */
-		unsigned char *str;
+		const unsigned char *str;
 		/* If @t==1: a pointer to a nested conversion table
 		 * (with 256 elements) that describes how to convert
 		 * each possible subsequent byte.  The conversion