Index: ObjFW.xcodeproj/project.pbxproj
==================================================================
--- ObjFW.xcodeproj/project.pbxproj
+++ ObjFW.xcodeproj/project.pbxproj
@@ -199,10 +199,12 @@
 		4BAF5F46123460C900F4E111 /* OFCollection.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = OFCollection.h; path = src/OFCollection.h; sourceTree = "<group>"; };
 		4BAF5F47123460C900F4E111 /* OFStreamObserver.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = OFStreamObserver.h; path = src/OFStreamObserver.h; sourceTree = "<group>"; };
 		4BAF5F48123460C900F4E111 /* OFStreamObserver.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; name = OFStreamObserver.m; path = src/OFStreamObserver.m; sourceTree = "<group>"; };
 		4BAF5F49123460C900F4E111 /* OFStreamSocket.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = OFStreamSocket.h; path = src/OFStreamSocket.h; sourceTree = "<group>"; };
 		4BAF5F4A123460C900F4E111 /* OFStreamSocket.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; name = OFStreamSocket.m; path = src/OFStreamSocket.m; sourceTree = "<group>"; };
+		4BB50DCF12F863C700C9393F /* of_asprintf.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = of_asprintf.h; path = src/of_asprintf.h; sourceTree = SOURCE_ROOT; };
+		4BB50DD012F863C700C9393F /* of_asprintf.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; name = of_asprintf.m; path = src/of_asprintf.m; sourceTree = SOURCE_ROOT; };
 		4BBA36C411406AB700CBA3AC /* atomic.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = atomic.h; path = src/atomic.h; sourceTree = "<group>"; };
 		4BBA36C511406AB700CBA3AC /* macros.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = macros.h; path = src/macros.h; sourceTree = "<group>"; };
 		4BD86D801237A6C600ED9912 /* OFBlock.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = OFBlock.h; path = src/OFBlock.h; sourceTree = SOURCE_ROOT; };
 		4BD86D811237A6C600ED9912 /* OFBlock.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; name = OFBlock.m; path = src/OFBlock.m; sourceTree = SOURCE_ROOT; };
 		4BE5F0D712DF4225005C7A0C /* OFConstantString.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = OFConstantString.h; path = src/OFConstantString.h; sourceTree = SOURCE_ROOT; };
@@ -327,10 +329,12 @@
 				4B6AF96F10A8D40E0003FB0A /* iso_8859_15.m */,
 				4BBA36C511406AB700CBA3AC /* macros.h */,
 				4B4986DF1101F64500A2CFDA /* objc_properties.m */,
 				4B6799581099E7C50041064A /* objc_sync.m */,
 				4BF1BCBF11C9663F0025511F /* objfw-defs.h.in */,
+				4BB50DCF12F863C700C9393F /* of_asprintf.h */,
+				4BB50DD012F863C700C9393F /* of_asprintf.m */,
 				4B67998B1099E7C50041064A /* threading.h */,
 				4B67998C1099E7C50041064A /* unicode.h */,
 				4BFBDD1610A0724800051AFB /* unicode.m */,
 				4B6AF97210A8D42E0003FB0A /* windows_1252.m */,
 			);

Index: tests/OFStringTests.m
==================================================================
--- tests/OFStringTests.m
+++ tests/OFStringTests.m
@@ -156,16 +156,16 @@
 					  "\x9C\x9E\x9F"
 				encoding: OF_STRING_ENCODING_WINDOWS_1252]
 	    isEqual: @"€‚ƒ„…†‡ˆ‰Š‹ŒŽ‘’“”•–—˜™š›œžŸ"])
 
 	TEST(@"+[stringWithFormat:]",
-	    [(s[0] = [OFMutableString stringWithFormat: @"%s: %d", "test", 123])
-	    isEqual: @"test: 123"])
+	    [(s[0] = [OFMutableString stringWithFormat: @"%@:%d", @"test", 123])
+	    isEqual: @"test:123"])
 
 	TEST(@"-[appendFormat:]",
 	    R(([s[0] appendFormat: @"%02X", 15])) &&
-	    [s[0] isEqual: @"test: 1230F"])
+	    [s[0] isEqual: @"test:1230F"])
 
 	TEST(@"+[stringWithPath:]",
 	    (s[0] = [OFString stringWithPath: @"foo", @"bar", @"baz", nil]) &&
 #ifndef _WIN32
 	    [s[0] isEqual: @"foo/bar/baz"] &&