Index: src/OFHTTPClient.m
==================================================================
--- src/OFHTTPClient.m
+++ src/OFHTTPClient.m
@@ -43,11 +43,11 @@
 #import "OFWriteFailedException.h"
 
 static OF_INLINE void
 normalizeKey(char *str_)
 {
-	uint8_t *str = (uint8_t*)str_;
+	unsigned char *str = (unsigned char*)str_;
 	bool firstLetter = true;
 
 	while (*str != '\0') {
 		if (!isalnum(*str)) {
 			firstLetter = true;

Index: src/OFHTTPServer.m
==================================================================
--- src/OFHTTPServer.m
+++ src/OFHTTPServer.m
@@ -144,11 +144,11 @@
 
 static OF_INLINE OFString*
 normalizedKey(OFString *key)
 {
 	char *cString = of_strdup([key UTF8String]);
-	uint8_t *tmp = (uint8_t*)cString;
+	unsigned char *tmp = (unsigned char*)cString;
 	bool firstLetter = true;
 
 	if (cString == NULL)
 		@throw [OFOutOfMemoryException
 		    exceptionWithRequestedSize: strlen([key UTF8String])];

Index: src/OFIntrospection.m
==================================================================
--- src/OFIntrospection.m
+++ src/OFIntrospection.m
@@ -275,11 +275,11 @@
 			of_unichar_t first = [_name characterAtIndex: 0];
 			OFMutableString *tmp = [_name mutableCopy];
 			_setter = tmp;
 
 			if (first < 0x80) {
-				[tmp setCharacter: toupper((int)first)
+				[tmp setCharacter: toupper((unsigned char)first)
 					  atIndex: 0];
 			}
 
 			[tmp prependString: @"set"];
 

Index: src/OFObject+KeyValueCoding.m
==================================================================
--- src/OFObject+KeyValueCoding.m
+++ src/OFObject+KeyValueCoding.m
@@ -62,11 +62,11 @@
 		@try {
 			memcpy(name, "is", 2);
 			memcpy(name + 2, [key UTF8String], keyLength);
 			name[keyLength + 2] = '\0';
 
-			name[2] = toupper(name[2]);
+			name[2] = toupper((unsigned char)name[2]);
 
 			selector = sel_registerName(name);
 		} @finally {
 			free(name);
 		}
@@ -144,11 +144,11 @@
 	@try {
 		memcpy(name, "set", 3);
 		memcpy(name + 3, [key UTF8String], keyLength);
 		memcpy(name + keyLength + 3, ":", 2);
 
-		name[3] = toupper(name[3]);
+		name[3] = toupper((unsigned char)name[3]);
 
 		selector = sel_registerName(name);
 	} @finally {
 		free(name);
 	}

Index: src/OFString_UTF8.m
==================================================================
--- src/OFString_UTF8.m
+++ src/OFString_UTF8.m
@@ -44,13 +44,15 @@
 
 static inline int
 memcasecmp(const char *first, const char *second, size_t length)
 {
 	for (size_t i = 0; i < length; i++) {
-		if (tolower((int)first[i]) > tolower((int)second[i]))
+		if (tolower((unsigned char)first[i]) >
+		    tolower((unsigned char)second[i]))
 			return OF_ORDERED_DESCENDING;
-		if (tolower((int)first[i]) < tolower((int)second[i]))
+		if (tolower((unsigned char)first[i]) <
+		    tolower((unsigned char)second[i]))
 			return OF_ORDERED_ASCENDING;
 	}
 
 	return OF_ORDERED_SAME;
 }

Index: src/OFURL.m
==================================================================
--- src/OFURL.m
+++ src/OFURL.m
@@ -83,11 +83,11 @@
 
 		if ((tmp = strstr(UTF8String, "://")) == NULL)
 			@throw [OFInvalidFormatException exception];
 
 		for (tmp2 = UTF8String; tmp2 < tmp; tmp2++)
-			*tmp2 = tolower((int)*tmp2);
+			*tmp2 = tolower((unsigned char)*tmp2);
 
 		_scheme = [[[OFString stringWithUTF8String: UTF8String
 						    length: tmp - UTF8String]
 		    stringByURLDecoding] copy];