Index: src/OFConstantString.m
==================================================================
--- src/OFConstantString.m
+++ src/OFConstantString.m
@@ -256,11 +256,11 @@
 
 	return [self mutableCopy];
 }
 
 /* From protocol OFComparing */
-- (of_comparison_result_t)compare: (id)object
+- (of_comparison_result_t)compare: (id <OFComparing>)object
 {
 	[self finishInitialization];
 
 	return [self compare: object];
 }

Index: src/OFDataArray.m
==================================================================
--- src/OFDataArray.m
+++ src/OFDataArray.m
@@ -378,21 +378,21 @@
 		return NO;
 
 	return YES;
 }
 
-- (of_comparison_result_t)compare: (id)object
+- (of_comparison_result_t)compare: (id <OFComparing>)object
 {
 	OFDataArray *otherDataArray;
 	int comparison;
 	size_t otherCount, minimumCount;
 
 	if (![object isKindOfClass: [OFDataArray class]])
 		@throw [OFInvalidArgumentException
 		    exceptionWithClass: [self class]
 			      selector: _cmd];
-	otherDataArray = object;
+	otherDataArray = (OFDataArray*)object;
 
 	if ([otherDataArray itemSize] != itemSize)
 		@throw [OFInvalidArgumentException
 		    exceptionWithClass: [self class]
 			      selector: _cmd];

Index: src/OFNumber.h
==================================================================
--- src/OFNumber.h
+++ src/OFNumber.h
@@ -61,11 +61,12 @@
 } of_number_type_t;
 
 /**
  * \brief Provides a way to store a number in an object.
  */
-@interface OFNumber: OFObject <OFCopying, OFSerialization, OFJSONRepresentation>
+@interface OFNumber: OFObject <OFCopying, OFComparing, OFSerialization,
+    OFJSONRepresentation>
 {
 	union of_number_value {
 		BOOL	       bool_;
 		signed char    char_;
 		signed short   short_;

Index: src/OFNumber.m
==================================================================
--- src/OFNumber.m
+++ src/OFNumber.m
@@ -935,10 +935,53 @@
 	if (type & OF_NUMBER_SIGNED || number->type & OF_NUMBER_SIGNED)
 		return ([number intMaxValue] == [self intMaxValue]);
 
 	return ([number uIntMaxValue] == [self uIntMaxValue]);
 }
+
+- (of_comparison_result_t)compare: (id)object
+{
+	OFNumber *number;
+
+	if (![object isKindOfClass: [OFNumber class]])
+		@throw [OFInvalidArgumentException
+		    exceptionWithClass: [self class]];
+
+	number = object;
+
+	if (type & OF_NUMBER_FLOAT || number->type & OF_NUMBER_FLOAT) {
+		double double1 = [self doubleValue];
+		double double2 = [number doubleValue];
+
+		if (double1 > double2)
+			return OF_ORDERED_DESCENDING;
+		if (double1 < double2)
+			return OF_ORDERED_ASCENDING;
+
+		return OF_ORDERED_SAME;
+	} else if (type & OF_NUMBER_SIGNED || number->type & OF_NUMBER_SIGNED) {
+		intmax_t int1 = [self intMaxValue];
+		intmax_t int2 = [number intMaxValue];
+
+		if (int1 > int2)
+			return OF_ORDERED_DESCENDING;
+		if (int1 < int2)
+			return OF_ORDERED_ASCENDING;
+
+		return OF_ORDERED_SAME;
+	} else {
+		uintmax_t uint1 = [self uIntMaxValue];
+		uintmax_t uint2 = [number uIntMaxValue];
+
+		if (uint1 > uint2)
+			return OF_ORDERED_DESCENDING;
+		if (uint1 < uint2)
+			return OF_ORDERED_ASCENDING;
+
+		return OF_ORDERED_SAME;
+	}
+}
 
 - (uint32_t)hash
 {
 	uint32_t hash;
 	uint8_t i;

Index: src/OFObject.h
==================================================================
--- src/OFObject.h
+++ src/OFObject.h
@@ -640,11 +640,11 @@
  * \brief Compares the object with another object.
  *
  * \param object An object to compare the object to
  * \return The result of the comparison
  */
-- (of_comparison_result_t)compare: (id)object;
+- (of_comparison_result_t)compare: (id <OFComparing>)object;
 @end
 
 #import "OFObject+Serialization.h"
 
 #ifdef __cplusplus

Index: src/OFString.m
==================================================================
--- src/OFString.m
+++ src/OFString.m
@@ -1139,11 +1139,11 @@
 - mutableCopy
 {
 	return [[OFMutableString alloc] initWithString: self];
 }
 
-- (of_comparison_result_t)compare: (id)object
+- (of_comparison_result_t)compare: (id <OFComparing>)object
 {
 	void *pool;
 	OFString *otherString;
 	const of_unichar_t *unicodeString, *otherUnicodeString;
 	size_t i, minimumLength;
@@ -1154,11 +1154,11 @@
 	if (![object isKindOfClass: [OFString class]])
 		@throw [OFInvalidArgumentException
 		    exceptionWithClass: [self class]
 			      selector: _cmd];
 
-	otherString = object;
+	otherString = (OFString*)object;
 	minimumLength = ([self length] > [otherString length]
 	    ? [otherString length] : [self length]);
 
 	pool = objc_autoreleasePoolPush();
 

Index: src/OFString_UTF8.m
==================================================================
--- src/OFString_UTF8.m
+++ src/OFString_UTF8.m
@@ -690,11 +690,11 @@
 		return NO;
 
 	return YES;
 }
 
-- (of_comparison_result_t)compare: (id)object
+- (of_comparison_result_t)compare: (id <OFComparing>)object
 {
 	OFString *otherString;
 	size_t otherCStringLength, minimumCStringLength;
 	int compare;
 
@@ -704,11 +704,11 @@
 	if (![object isKindOfClass: [OFString class]])
 		@throw [OFInvalidArgumentException
 		    exceptionWithClass: [self class]
 			      selector: _cmd];
 
-	otherString = object;
+	otherString = (OFString*)object;
 	otherCStringLength = [otherString UTF8StringLength];
 	minimumCStringLength = (s->cStringLength > otherCStringLength
 	    ? otherCStringLength : s->cStringLength);
 
 	if ((compare = memcmp(s->cString, [otherString UTF8String],