diff --git a/Source/NSKeyedArchiver.m b/Source/NSKeyedArchiver.m
index 18e3d118f..efbb47d7f 100644
--- a/Source/NSKeyedArchiver.m
+++ b/Source/NSKeyedArchiver.m
@@ -556,6 +556,17 @@ static NSDictionary *makeReference(unsigned ref)
   return _delegate;
 }
 
+- (NSString*) description
+{
+  if (_data == nil)
+    {
+      // For consistency with OSX
+      [NSException raise: NSInvalidArgumentException
+		  format: @"method sent to uninitialised archiver"];
+    }
+  return [super description];
+}
+
 - (void) encodeArrayOfObjCType: (const char*)aType
 			 count: (NSUInteger)aCount
 			    at: (const void*)address
diff --git a/Source/NSKeyedUnarchiver.m b/Source/NSKeyedUnarchiver.m
index f73db8a30..c12eeab59 100644
--- a/Source/NSKeyedUnarchiver.m
+++ b/Source/NSKeyedUnarchiver.m
@@ -749,6 +749,17 @@ static NSMapTable	*globalClassMap = 0;
   return _delegate;
 }
 
+- (NSString*) description
+{
+  if (_archive == nil)
+    {
+      // For consistency with OSX
+      [NSException raise: NSInvalidArgumentException
+		  format: @"method sent to uninitialised unarchiver"];
+    }
+  return [super description];
+}
+
 - (void) finishDecoding
 {
   [_delegate unarchiverWillFinish: self];