Index: src/OFString.m
==================================================================
--- src/OFString.m
+++ src/OFString.m
@@ -1034,10 +1034,13 @@
 {
 	OFAutoreleasePool *pool;
 	OFString *otherString;
 	const of_unichar_t *unicodeString, *otherUnicodeString;
 	size_t length;
+
+	if (object == self)
+		return YES;
 
 	if (![object isKindOfClass: [OFString class]])
 		return NO;
 
 	otherString = object;
@@ -1077,10 +1080,13 @@
 	OFAutoreleasePool *pool;
 	OFString *otherString;
 	const of_unichar_t *unicodeString, *otherUnicodeString;
 	size_t i, minimumLength;
 
+	if (object == self)
+		return OF_ORDERED_SAME;
+
 	if (![object isKindOfClass: [OFString class]])
 		@throw [OFInvalidArgumentException exceptionWithClass: isa
 							     selector: _cmd];
 
 	otherString = object;
@@ -1117,10 +1123,13 @@
 - (of_comparison_result_t)caseInsensitiveCompare: (OFString*)otherString
 {
 	OFAutoreleasePool *pool = [[OFAutoreleasePool alloc] init];
 	const of_unichar_t *string, *otherUnicodeString;
 	size_t i, length, otherLength, minimumLength;
+
+	if (otherString == self)
+		return OF_ORDERED_SAME;
 
 	string = [self unicodeString];
 	otherUnicodeString = [otherString unicodeString];
 	length = [self length];
 	otherLength = [otherString length];

Index: src/OFString_UTF8.m
==================================================================
--- src/OFString_UTF8.m
+++ src/OFString_UTF8.m
@@ -587,10 +587,13 @@
 }
 
 - (BOOL)isEqual: (id)object
 {
 	OFString_UTF8 *otherString;
+
+	if (object == self)
+		return YES;
 
 	if (![object isKindOfClass: [OFString class]])
 		return NO;
 
 	otherString = object;
@@ -609,10 +612,13 @@
 {
 	OFString *otherString;
 	size_t otherCStringLength, minimumCStringLength;
 	int compare;
 
+	if (object == self)
+		return OF_ORDERED_SAME;
+
 	if (![object isKindOfClass: [OFString class]])
 		@throw [OFInvalidArgumentException exceptionWithClass: isa
 							     selector: _cmd];
 
 	otherString = object;
@@ -638,10 +644,13 @@
 - (of_comparison_result_t)caseInsensitiveCompare: (OFString*)otherString
 {
 	const char *otherCString;
 	size_t i, j, otherCStringLength, minimumCStringLength;
 	int compare;
+
+	if (otherString == self)
+		return OF_ORDERED_SAME;
 
 	if (![otherString isKindOfClass: [OFString class]])
 		@throw [OFInvalidArgumentException exceptionWithClass: isa
 							     selector: _cmd];