@@ -1422,106 +1422,78 @@
 	OFMutableString *new;
 
 	new = [OFMutableString stringWithString: self];
 	[new appendString: string];
 
-	/*
-	 * Class swizzle the string to be immutable. We declared the return type
-	 * to be OFString*, so it can't be modified anyway. But not swizzling it
-	 * would create a real copy each time -[copy] is called.
-	 */
-	new->isa = [OFString class];
+	[new makeImmutable];
+
 	return new;
 }
 
 - (OFString*)stringByPrependingString: (OFString*)string
 {
 	OFMutableString *new = [[string mutableCopy] autorelease];
 
 	[new appendString: self];
 
-	/*
-	 * Class swizzle the string to be immutable. We declared the return type
-	 * to be OFString*, so it can't be modified anyway. But not swizzling it
-	 * would create a real copy each time -[copy] is called.
-	 */
-	new->isa = [OFString class];
+	[new makeImmutable];
+
 	return new;
 }
 
 - (OFString*)uppercaseString
 {
 	OFMutableString *new = [[self mutableCopy] autorelease];
 
 	[new upper];
 
-	/*
-	 * Class swizzle the string to be immutable. We declared the return type
-	 * to be OFString*, so it can't be modified anyway. But not swizzling it
-	 * would create a real copy each time -[copy] is called.
-	 */
-	new->isa = [OFString class];
+	[new makeImmutable];
+
 	return new;
 }
 
 - (OFString*)lowercaseString
 {
 	OFMutableString *new = [[self mutableCopy] autorelease];
 
 	[new lower];
 
-	/*
-	 * Class swizzle the string to be immutable. We declared the return type
-	 * to be OFString*, so it can't be modified anyway. But not swizzling it
-	 * would create a real copy each time -[copy] is called.
-	 */
-	new->isa = [OFString class];
+	[new makeImmutable];
+
 	return new;
 }
 
 - (OFString*)stringByDeletingLeadingWhitespaces
 {
 	OFMutableString *new = [[self mutableCopy] autorelease];
 
 	[new deleteLeadingWhitespaces];
 
-	/*
-	 * Class swizzle the string to be immutable. We declared the return type
-	 * to be OFString*, so it can't be modified anyway. But not swizzling it
-	 * would create a real copy each time -[copy] is called.
-	 */
-	new->isa = [OFString class];
+	[new makeImmutable];
+
 	return new;
 }
 
 - (OFString*)stringByDeletingTrailingWhitespaces
 {
 	OFMutableString *new = [[self mutableCopy] autorelease];
 
 	[new deleteTrailingWhitespaces];
 
-	/*
-	 * Class swizzle the string to be immutable. We declared the return type
-	 * to be OFString*, so it can't be modified anyway. But not swizzling it
-	 * would create a real copy each time -[copy] is called.
-	 */
-	new->isa = [OFString class];
+	[new makeImmutable];
+
 	return new;
 }
 
 - (OFString*)stringByDeletingEnclosingWhitespaces
 {
 	OFMutableString *new = [[self mutableCopy] autorelease];
 
 	[new deleteEnclosingWhitespaces];
 
-	/*
-	 * Class swizzle the string to be immutable. We declared the return type
-	 * to be OFString*, so it can't be modified anyway. But not swizzling it
-	 * would create a real copy each time -[copy] is called.
-	 */
-	new->isa = [OFString class];
+	[new makeImmutable];
+
 	return new;
 }
 
 - (BOOL)hasPrefix: (OFString*)prefix
 {
@@ -1571,13 +1543,15 @@
 		i += cStringLength - 1;
 		last = i + 1;
 	}
 	[array addObject: [OFString stringWithCString: s->cString + last]];
 
+	[array makeImmutable];
+
 	[pool release];
 
-	return [array makeImmutable];
+	return array;
 }
 
 - (OFArray*)pathComponents
 {
 	OFMutableArray *ret;
@@ -1613,13 +1587,15 @@
 	}
 
 	[ret addObject: [OFString stringWithCString: s->cString + last
 					     length: i - last]];
 
+	[ret makeImmutable];
+
 	[pool release];
 
-	return [ret makeImmutable];
+	return ret;
 }
 
 - (OFString*)lastPathComponent
 {
 	size_t pathCStringLength = s->cStringLength;