Index: src/OFDictionary.m
==================================================================
--- src/OFDictionary.m
+++ src/OFDictionary.m
@@ -615,15 +615,20 @@
 
 		i = 0;
 		while ((key = [keyEnumerator nextObject]) != nil &&
 		    (object = [objectEnumerator nextObject]) != nil) {
 			void *pool2 = objc_autoreleasePoolPush();
+			int identifierOptions =
+			    options | OF_JSON_REPRESENTATION_IDENTIFIER;
+
+			if (![key isKindOfClass: [OFString class]])
+				@throw [OFInvalidArgumentException exception];
 
 			[JSON appendString: indentation];
 			[JSON appendString: @"\t"];
 			[JSON appendString: [key
-			    OF_JSONRepresentationWithOptions: options
+			    OF_JSONRepresentationWithOptions: identifierOptions
 						       depth: depth + 1]];
 			[JSON appendString: @": "];
 			[JSON appendString: [object
 			    OF_JSONRepresentationWithOptions: options
 						       depth: depth + 1]];
@@ -640,13 +645,18 @@
 	} else {
 		i = 0;
 		while ((key = [keyEnumerator nextObject]) != nil &&
 		    (object = [objectEnumerator nextObject]) != nil) {
 			void *pool2 = objc_autoreleasePoolPush();
+			int identifierOptions =
+			    options | OF_JSON_REPRESENTATION_IDENTIFIER;
+
+			if (![key isKindOfClass: [OFString class]])
+				@throw [OFInvalidArgumentException exception];
 
 			[JSON appendString: [key
-			    OF_JSONRepresentationWithOptions: options
+			    OF_JSONRepresentationWithOptions: identifierOptions
 						       depth: depth + 1]];
 			[JSON appendString: @":"];
 			[JSON appendString: [object
 			    OF_JSONRepresentationWithOptions: options
 						       depth: depth + 1]];

Index: src/OFJSONRepresentation.h
==================================================================
--- src/OFJSONRepresentation.h
+++ src/OFJSONRepresentation.h
@@ -15,11 +15,13 @@
  */
 
 @class OFString;
 
 enum {
-	OF_JSON_REPRESENTATION_PRETTY = 1
+	OF_JSON_REPRESENTATION_PRETTY	  = 0x01,
+	OF_JSON_REPRESENTATION_JSON5	  = 0x02,
+	OF_JSON_REPRESENTATION_IDENTIFIER = 0x10
 };
 
 /*!
  * @brief A protocol implemented by classes that support encoding to a JSON
  *	  representation.
@@ -42,10 +44,11 @@
  * @param options The options to use when creating a JSON representation.@n
  *		  Possible values are:
  *		  Value                           | Description
  *		  --------------------------------|-------------------------
  *		  `OF_JSON_REPRESENTATION_PRETTY` | Optimize for readability
+ *		  `OF_JSON_REPRESENTATION_JSON5`  | Generate JSON5
  *
  * @return The JSON representation of the object as a string
  */
 - (OFString*)JSONRepresentationWithOptions: (int)options;
 @end

Index: src/OFNumber.m
==================================================================
--- src/OFNumber.m
+++ src/OFNumber.m
@@ -1422,14 +1422,17 @@
 	if (_type == OF_NUMBER_BOOL)
 		return (_value.bool_ ? @"true" : @"false");
 
 	doubleValue = [self doubleValue];
 	if (isinf(doubleValue)) {
-		if (doubleValue > 0)
-			return @"Infinity";
-		else
-			return @"-Infinity";
+		if (options & OF_JSON_REPRESENTATION_JSON5) {
+			if (doubleValue > 0)
+				return @"Infinity";
+			else
+				return @"-Infinity";
+		} else
+			@throw [OFInvalidArgumentException exception];
 	}
 
 	return [self description];
 }
 

Index: src/OFString.m
==================================================================
--- src/OFString.m
+++ src/OFString.m
@@ -17,10 +17,11 @@
 #include "config.h"
 
 #include <stdarg.h>
 #include <stdlib.h>
 #include <string.h>
+#include <ctype.h>
 
 #include <sys/stat.h>
 
 #import "OFString.h"
 #import "OFString_UTF8.h"
@@ -1458,19 +1459,39 @@
 			      withString: @"\\\""];
 	[JSON replaceOccurrencesOfString: @"\b"
 			      withString: @"\\b"];
 	[JSON replaceOccurrencesOfString: @"\f"
 			      withString: @"\\f"];
-	[JSON replaceOccurrencesOfString: @"\n"
-			      withString: @"\\n"];
 	[JSON replaceOccurrencesOfString: @"\r"
 			      withString: @"\\r"];
 	[JSON replaceOccurrencesOfString: @"\t"
 			      withString: @"\\t"];
 
-	[JSON prependString: @"\""];
-	[JSON appendString: @"\""];
+	if (options & OF_JSON_REPRESENTATION_JSON5) {
+		[JSON replaceOccurrencesOfString: @"\n"
+				      withString: @"\\\n"];
+
+		if (options & OF_JSON_REPRESENTATION_IDENTIFIER) {
+			const char *cString = [self UTF8String];
+
+			if ((!isalpha(cString[0]) && cString[0] != '_' &&
+			    cString[0] != '$') ||
+			    strpbrk(cString, " \n\r\t\b\f\\\"'") != NULL) {
+				[JSON prependString: @"\""];
+				[JSON appendString: @"\""];
+			}
+		} else {
+			[JSON prependString: @"\""];
+			[JSON appendString: @"\""];
+		}
+	} else {
+		[JSON replaceOccurrencesOfString: @"\n"
+				      withString: @"\\n"];
+
+		[JSON prependString: @"\""];
+		[JSON appendString: @"\""];
+	}
 
 	[JSON makeImmutable];
 
 	return JSON;
 }