Index: src/OFDictionary.h
==================================================================
--- src/OFDictionary.h
+++ src/OFDictionary.h
@@ -55,11 +55,11 @@
  * Sets a key to an object. A key can be any object.
  *
  * \param key The key to set
  * \param obj The object to set the key to
  */
-- set: (OFObject*)key
+- set: (OFObject <OFCopying>*)key
    to: (OFObject*)obj;
 
 /**
  * \param key The key whose object should be returned
  * \return The object for the given key or nil if the key was not found

Index: src/OFDictionary.m
==================================================================
--- src/OFDictionary.m
+++ src/OFDictionary.m
@@ -97,15 +97,15 @@
 			[data[i] release];
 
 	[super dealloc];
 }
 
-- set: (OFObject*)key
+- set: (OFObject <OFCopying>*)key
    to: (OFObject*)obj
 {
 	uint32_t hash;
-	of_list_object_t *iter;
+	of_list_object_t *iter, *key_obj;
 
 	if (key == nil || obj == nil)
 		@throw [OFInvalidArgumentException newWithClass: isa
 						    andSelector: _cmd];
 
@@ -122,12 +122,23 @@
 
 			return self;
 		}
 	}
 
-	[data[hash] append: key];
-	[data[hash] append: obj];
+	key = [key copy];
+	@try {
+		key_obj = [data[hash] append: key];
+	} @finally {
+		[key release];
+	}
+
+	@try {
+		[data[hash] append: obj];
+	} @catch (OFException *e) {
+		[data[hash] remove: key_obj];
+		@throw e;
+	}
 
 	return self;
 }
 
 - (id)get: (OFObject*)key