Index: src/OFConstantString.m
==================================================================
--- src/OFConstantString.m
+++ src/OFConstantString.m
@@ -391,10 +391,19 @@
 {
 	[self finishInitialization];
 
 	return [self stringByAppendingString: string];
 }
+
+- (OFString*)stringByAppendingFormat: (OFConstantString*)format
+			   arguments: (va_list)arguments
+{
+	[self finishInitialization];
+
+	return [self stringByAppendingFormat: format
+				   arguments: arguments];
+}
 
 - (OFString*)stringByAppendingPathComponent: (OFString*)component
 {
 	[self finishInitialization];
 

Index: src/OFString.h
==================================================================
--- src/OFString.h
+++ src/OFString.h
@@ -687,10 +687,20 @@
  * @param format A format string which generates the string to append
  * @return A new, autoreleased OFString with the specified format appended
  */
 - (OFString*)stringByAppendingFormat: (OFConstantString*)format, ...;
 
+/*!
+ * @brief Creates a new string by appending the specified format.
+ *
+ * @param format A format string which generates the string to append
+ * @param arguments The arguments used in the format string
+ * @return A new, autoreleased OFString with the specified format appended
+ */
+- (OFString*)stringByAppendingFormat: (OFConstantString*)format
+			   arguments: (va_list)arguments;
+
 /*!
  * @brief Creates a new string by appending a path component.
  *
  * @param component The path component to append
  * @return A new, autoreleased OFString with the path component appended

Index: src/OFString.m
==================================================================
--- src/OFString.m
+++ src/OFString.m
@@ -1347,19 +1347,29 @@
 	return new;
 }
 
 - (OFString*)stringByAppendingFormat: (OFConstantString*)format, ...
 {
-	OFMutableString *new;
+	OFString *ret;
 	va_list arguments;
 
-	new = [OFMutableString stringWithString: self];
-
 	va_start(arguments, format);
+	ret = [self stringByAppendingFormat: format
+				  arguments: arguments];
+	va_end(arguments);
+
+	return ret;
+}
+
+- (OFString*)stringByAppendingFormat: (OFConstantString*)format
+			   arguments: (va_list)arguments
+{
+	OFMutableString *new;
+
+	new = [OFMutableString stringWithString: self];
 	[new appendFormat: format
 		arguments: arguments];
-	va_end(arguments);
 
 	[new makeImmutable];
 
 	return new;
 }