diff --git a/lib/util/charset/charcnv.c b/lib/util/charset/charcnv.c
index e9f6ab0..4e46cfc 100644
--- a/lib/util/charset/charcnv.c
+++ b/lib/util/charset/charcnv.c
@@ -135,21 +135,6 @@ static smb_iconv_t get_conv_handle(struct smb_iconv_convenience *ic,
 				   charset_t from, charset_t to)
 {
 	const char *n1, *n2;
-	static bool initialised;
-
-	if (initialised == false) {
-		initialised = true;
-		
-#ifdef LC_ALL
-		/* we set back the locale to C to get ASCII-compatible
-		   toupper/lower functions.  For now we do not need
-		   any other POSIX localisations anyway. When we
-		   should really need localized string functions one
-		   day we need to write our own ascii_tolower etc.
-		*/
-		setlocale(LC_ALL, "C");
-#endif
-	}
 
 	if (ic->conv_handles[from][to]) {
 		return ic->conv_handles[from][to];
diff --git a/lib/util/charset/codepoints.c b/lib/util/charset/codepoints.c
index 8be2051..fe7ea36 100644
--- a/lib/util/charset/codepoints.c
+++ b/lib/util/charset/codepoints.c
@@ -69,7 +69,9 @@ void load_case_tables(void)
 _PUBLIC_ codepoint_t toupper_m(codepoint_t val)
 {
 	if (val < 128) {
-		return toupper(val);
+		if (val >= 'a' && val <= 'z')
+			val -= 32;
+		return val;
 	}
 	if (upcase_table == NULL) {
 		load_case_tables();
@@ -89,7 +91,9 @@ _PUBLIC_ codepoint_t toupper_m(codepoint_t val)
 _PUBLIC_ codepoint_t tolower_m(codepoint_t val)
 {
 	if (val < 128) {
-		return tolower(val);
+		if (val >= 'A' && val <= 'Z')
+			val += 32;
+		return val;
 	}
 	if (lowcase_table == NULL) {
 		load_case_tables();
diff --git a/lib/util/charset/util_unistr.c b/lib/util/charset/util_unistr.c
index 520ce05..5e5edb7 100644
--- a/lib/util/charset/util_unistr.c
+++ b/lib/util/charset/util_unistr.c
@@ -542,7 +542,8 @@ _PUBLIC_ void strlower_m(char *s)
 	   supported multi-byte character sets are ascii-compatible
 	   (ie. they match for the first 128 chars) */
 	while (*s && !(((uint8_t)*s) & 0x80)) {
-		*s = tolower((uint8_t)*s);
+		if (*s >= 'A' && *s <= 'Z')
+			*s = (*s) + 32;
 		s++;
 	}
 
@@ -581,7 +582,8 @@ _PUBLIC_ void strupper_m(char *s)
 	   supported multi-byte character sets are ascii-compatible
 	   (ie. they match for the first 128 chars) */
 	while (*s && !(((uint8_t)*s) & 0x80)) {
-		*s = toupper((uint8_t)*s);
+		if (*s >= 'a' && *s <= 'z')
+			*s = (*s) - 32;
 		s++;
 	}