Index: src/OFDate.h
==================================================================
--- src/OFDate.h
+++ src/OFDate.h
@@ -16,10 +16,11 @@
 
 #import "OFObject.h"
 #import "OFSerialization.h"
 
 @class OFString;
+@class OFConstantString;
 
 /**
  * \brief A class for storing, accessing and comparing dates.
  */
 @interface OFDate: OFObject <OFCopying, OFComparing, OFSerialization>
@@ -239,24 +240,24 @@
 /**
  * \brief Creates a string of the date with the specified format.
  *
  * See the manpage for strftime for information on the format.
  *
- * \param fmt The format for the date string
+ * \param format The format for the date string
  * \return A new, autoreleased OFString
  */
-- (OFString*)dateStringWithFormat: (OFString*)fmt;
+- (OFString*)dateStringWithFormat: (OFConstantString*)format;
 
 /**
  * \brief Creates a string of the local date with the specified format.
  *
  * See the manpage for strftime for information on the format.
  *
- * \param fmt The format for the date string
+ * \param format The format for the date string
  * \return A new, autoreleased OFString
  */
-- (OFString*)localDateStringWithFormat: (OFString*)fmt;
+- (OFString*)localDateStringWithFormat: (OFConstantString*)format;
 
 /**
  * \brief Returns the earlier of the two dates.
  *
  * \param date Another date

Index: src/OFDate.m
==================================================================
--- src/OFDate.m
+++ src/OFDate.m
@@ -441,11 +441,11 @@
 - (uint16_t)localDayOfYear
 {
 	LOCALTIME_RET(tm_yday + 1)
 }
 
-- (OFString*)dateStringWithFormat: (OFString*)format
+- (OFString*)dateStringWithFormat: (OFConstantString*)format
 {
 	OFString *ret;
 	time_t seconds_ = (time_t)seconds;
 	struct tm tm;
 	char *buffer;
@@ -487,11 +487,11 @@
 	}
 
 	return ret;
 }
 
-- (OFString*)localDateStringWithFormat: (OFString*)format
+- (OFString*)localDateStringWithFormat: (OFConstantString*)format
 {
 	OFString *ret;
 	time_t seconds_ = (time_t)seconds;
 	struct tm tm;
 	char *buffer;

Index: src/OFMutableString.h
==================================================================
--- src/OFMutableString.h
+++ src/OFMutableString.h
@@ -95,21 +95,21 @@
  *
  * See printf for the format syntax.
  *
  * \param format A format string which generates the string to append
  */
-- (void)appendFormat: (OFString*)format, ...;
+- (void)appendFormat: (OFConstantString*)format, ...;
 
 /**
  * \brief Appends a formatted string to the OFMutableString.
  *
  * See printf for the format syntax.
  *
  * \param format A format string which generates the string to append
  * \param arguments The arguments used in the format string
  */
-- (void)appendFormat: (OFString*)format
+- (void)appendFormat: (OFConstantString*)format
        withArguments: (va_list)arguments;
 
 /**
  * \brief Prepends another OFString to the OFMutableString.
  *

Index: src/OFMutableString.m
==================================================================
--- src/OFMutableString.m
+++ src/OFMutableString.m
@@ -255,21 +255,21 @@
 						       selector: _cmd];
 
 	[self appendCString: [string_ cString]];
 }
 
-- (void)appendFormat: (OFString*)format, ...
+- (void)appendFormat: (OFConstantString*)format, ...
 {
 	va_list arguments;
 
 	va_start(arguments, format);
 	[self appendFormat: format
 	     withArguments: arguments];
 	va_end(arguments);
 }
 
-- (void)appendFormat: (OFString*)format
+- (void)appendFormat: (OFConstantString*)format
        withArguments: (va_list)arguments
 {
 	char *t;
 	int len;
 

Index: src/OFStream.h
==================================================================
--- src/OFStream.h
+++ src/OFStream.h
@@ -670,20 +670,20 @@
  * Writes a formatted string into the stream.
  *
  * \param format A string used as format
  * \return The number of bytes written
  */
-- (size_t)writeFormat: (OFString*)format, ...;
+- (size_t)writeFormat: (OFConstantString*)format, ...;
 
 /**
  * Writes a formatted string into the stream.
  *
  * \param format A string used as format
  * \param arguments The arguments used in the format string
  * \return The number of bytes written
  */
-- (size_t)writeFormat: (OFString*)format
+- (size_t)writeFormat: (OFConstantString*)format
 	withArguments: (va_list)arguments;
 
 /**
  * \return The number of bytes still present in the internal cache.
  */

Index: src/OFStream.m
==================================================================
--- src/OFStream.m
+++ src/OFStream.m
@@ -1269,11 +1269,11 @@
 	}
 
 	return stringLength + 1;
 }
 
-- (size_t)writeFormat: (OFString*)format, ...
+- (size_t)writeFormat: (OFConstantString*)format, ...
 {
 	va_list arguments;
 	size_t ret;
 
 	va_start(arguments, format);
@@ -1282,11 +1282,11 @@
 	va_end(arguments);
 
 	return ret;
 }
 
-- (size_t)writeFormat: (OFString*)format
+- (size_t)writeFormat: (OFConstantString*)format
 	withArguments: (va_list)arguments
 {
 	char *cString;
 	int length;
 

Index: src/OFString.h
==================================================================
--- src/OFString.h
+++ src/OFString.h
@@ -18,10 +18,12 @@
 #include <stdarg.h>
 #include <inttypes.h>
 
 #import "OFObject.h"
 #import "OFSerialization.h"
+
+@class OFConstantString;
 
 typedef uint32_t of_unichar_t;
 
 /**
  * \brief The encoding of a string.
@@ -207,11 +209,11 @@
  * See printf for the format syntax.
  *
  * \param format A string used as format to initialize the OFString
  * \return A new autoreleased OFString
  */
-+ stringWithFormat: (OFString*)format, ...;
++ stringWithFormat: (OFConstantString*)format, ...;
 
 /**
  * Creates a new OFString containing the constructed specified path.
  *
  * \param firstComponent The first component of the path
@@ -405,21 +407,21 @@
  * See printf for the format syntax.
  *
  * \param format A string used as format to initialize the OFString
  * \return An initialized OFString
  */
-- initWithFormat: (OFString*)format, ...;
+- initWithFormat: (OFConstantString*)format, ...;
 
 /**
  * Initializes an already allocated OFString with a format string.
  * See printf for the format syntax.
  *
  * \param format A string used as format to initialize the OFString
  * \param arguments The arguments used in the format string
  * \return An initialized OFString
  */
-- initWithFormat: (OFString*)format
+- initWithFormat: (OFConstantString*)format
        arguments: (va_list)arguments;
 
 /**
  * Initializes an already allocated OFString with the constructed specified
  * path.

Index: src/OFString.m
==================================================================
--- src/OFString.m
+++ src/OFString.m
@@ -362,11 +362,11 @@
 	return [[[self alloc] initWithUTF16String: string
 					byteOrder: byteOrder
 					   length: length] autorelease];
 }
 
-+ stringWithFormat: (OFString*)format, ...
++ stringWithFormat: (OFConstantString*)format, ...
 {
 	id ret;
 	va_list arguments;
 
 	va_start(arguments, format);
@@ -834,11 +834,11 @@
 	}
 
 	return self;
 }
 
-- initWithFormat: (OFString*)format, ...
+- initWithFormat: (OFConstantString*)format, ...
 {
 	id ret;
 	va_list arguments;
 
 	va_start(arguments, format);
@@ -847,11 +847,11 @@
 	va_end(arguments);
 
 	return ret;
 }
 
-- initWithFormat: (OFString*)format
+- initWithFormat: (OFConstantString*)format
        arguments: (va_list)arguments
 {
 	self = [super init];
 
 	@try {