Index: src/OFBitSetCharacterSet.m
==================================================================
--- src/OFBitSetCharacterSet.m
+++ src/OFBitSetCharacterSet.m
@@ -38,18 +38,19 @@
 		size_t length = string.length;
 
 		for (size_t i = 0; i < length; i++) {
 			of_unichar_t c = characters[i];
 
-			if (c / 8 >= _size) {
+			if (c / CHAR_BIT >= _size) {
 				size_t newSize;
 
 				if (UINT32_MAX - c < 1)
 					@throw [OFOutOfRangeException
 					    exception];
 
-				newSize = OF_ROUND_UP_POW2(8, c + 1) / 8;
+				newSize = OF_ROUND_UP_POW2(CHAR_BIT, c + 1) /
+				    CHAR_BIT;
 
 				_bitset = of_realloc(_bitset, newSize, 1);
 				memset(_bitset + _size, '\0', newSize - _size);
 
 				_size = newSize;
@@ -74,11 +75,11 @@
 	[super dealloc];
 }
 
 - (bool)characterIsMember: (of_unichar_t)character
 {
-	if (character / 8 >= _size)
+	if (character / CHAR_BIT >= _size)
 		return false;
 
 	return of_bitset_isset(_bitset, character);
 }
 @end

Index: src/OFSecureData.m
==================================================================
--- src/OFSecureData.m
+++ src/OFSecureData.m
@@ -99,11 +99,12 @@
 
 static struct page *
 addPage(bool allowPreallocated)
 {
 	size_t pageSize = [OFSystemInfo pageSize];
-	size_t mapSize = OF_ROUND_UP_POW2(8, pageSize / CHUNK_SIZE) / 8;
+	size_t mapSize = OF_ROUND_UP_POW2(CHAR_BIT, pageSize / CHUNK_SIZE) /
+	    CHAR_BIT;
 	struct page *page;
 # if !defined(OF_HAVE_COMPILER_TLS) && defined(OF_HAVE_THREADS)
 	struct page *lastPage;
 # endif
 
@@ -184,11 +185,12 @@
 static void
 removePageIfEmpty(struct page *page)
 {
 	unsigned char *map = page->map;
 	size_t pageSize = [OFSystemInfo pageSize];
-	size_t mapSize = OF_ROUND_UP_POW2(8, pageSize / CHUNK_SIZE) / 8;
+	size_t mapSize = OF_ROUND_UP_POW2(CHAR_BIT, pageSize / CHUNK_SIZE) /
+	    CHAR_BIT;
 
 	for (size_t i = 0; i < mapSize; i++)
 		if (map[i] != 0)
 			return;
 

Index: src/macros.h
==================================================================
--- src/macros.h
+++ src/macros.h
@@ -25,10 +25,11 @@
 #endif
 #ifndef __STDC_CONSTANT_MACROS
 # define __STDC_CONSTANT_MACROS
 #endif
 
+#include <limits.h>
 #include <stdbool.h>
 #include <stddef.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -822,23 +823,23 @@
 	}
 
 static OF_INLINE bool
 of_bitset_isset(unsigned char *_Nonnull storage, size_t idx)
 {
-	return storage[idx / 8] & (1u << (idx % 8));
+	return storage[idx / CHAR_BIT] & (1u << (idx % CHAR_BIT));
 }
 
 static OF_INLINE void
 of_bitset_set(unsigned char *_Nonnull storage, size_t idx)
 {
-	storage[idx / 8] |= (1u << (idx % 8));
+	storage[idx / CHAR_BIT] |= (1u << (idx % CHAR_BIT));
 }
 
 static OF_INLINE void
 of_bitset_clear(unsigned char *_Nonnull storage, size_t idx)
 {
-	storage[idx / 8] &= ~(1u << (idx % 8));
+	storage[idx / CHAR_BIT] &= ~(1u << (idx % CHAR_BIT));
 }
 
 static OF_INLINE char *_Nullable
 of_strdup(const char *_Nonnull string)
 {