Index: src/OFArray_adjacent.m
==================================================================
--- src/OFArray_adjacent.m
+++ src/OFArray_adjacent.m
@@ -288,13 +288,12 @@
 {
 	OFArray *otherArray;
 	id const *objects, *otherObjects;
 	size_t i, count;
 
-	if ([object class] != [OFArray_adjacent class] &&
-	    [object class] != [OFMutableArray_adjacent class] &&
-	    [object class] != [OFArray_adjacentSubarray class])
+	if (![object isKindOfClass: [OFArray_adjacent class]] &&
+	    ![object isKindOfClass: [OFMutableArray_adjacent class]])
 		return [super isEqual: object];
 
 	otherArray = object;
 
 	count = [_array count];

Index: src/OFArray_adjacentSubarray.m
==================================================================
--- src/OFArray_adjacentSubarray.m
+++ src/OFArray_adjacentSubarray.m
@@ -30,13 +30,12 @@
 {
 	OFArray *otherArray;
 	id const *objects, *otherObjects;
 	size_t i;
 
-	if ([object class] != [OFArray_adjacent class] &&
-	    [object class] != [OFMutableArray_adjacent class] &&
-	    [object class] != [OFArray_adjacentSubarray class])
+	if (![object isKindOfClass: [OFArray_adjacent class]] &&
+	    ![object isKindOfClass: [OFMutableArray_adjacent class]])
 		return [super isEqual: object];
 
 	otherArray = object;
 
 	if (_range.length != [otherArray count])

Index: src/OFDictionary_hashtable.m
==================================================================
--- src/OFDictionary_hashtable.m
+++ src/OFDictionary_hashtable.m
@@ -101,12 +101,12 @@
 	size_t count;
 
 	if (dictionary == nil)
 		return [self init];
 
-	if ([dictionary class] == [OFDictionary_hashtable class] ||
-	    [dictionary class] == [OFMutableDictionary_hashtable class]) {
+	if ([dictionary isKindOfClass: [OFDictionary_hashtable class]] ||
+	    [dictionary isKindOfClass: [OFMutableDictionary_hashtable class]]) {
 		self = [super init];
 
 		@try {
 			OFDictionary_hashtable *dictionary_ =
 			    (OFDictionary_hashtable*)dictionary;
@@ -312,12 +312,12 @@
 
 - (bool)isEqual: (id)dictionary
 {
 	OFDictionary_hashtable *dictionary_;
 
-	if ([self class] != [OFDictionary_hashtable class] &&
-	    [self class] != [OFMutableDictionary_hashtable class])
+	if (![dictionary isKindOfClass: [OFDictionary_hashtable class]] &&
+	    ![dictionary isKindOfClass: [OFMutableDictionary_hashtable class]])
 		return [super isEqual: dictionary];
 
 	dictionary_ = (OFDictionary_hashtable*)dictionary;
 
 	return [dictionary_->_mapTable isEqual: _mapTable];