diff --git a/Source/Stream.m b/Source/Stream.m
index 88e864949..ecd1941a2 100644
--- a/Source/Stream.m
+++ b/Source/Stream.m
@@ -57,12 +57,26 @@
   return 0;
 }
 
+- (int) writeFormat: (id <String>)format
+	  arguments: (va_list)arg
+{
+  [self subclassResponsibility:_cmd];
+  return 0;
+}
+
 - (int) writeFormat: (id <String>)format, ...
 {
   [self subclassResponsibility:_cmd];
   return 0;
 }
 
+- (int) readFormat: (id <String>)format
+	 arguments: (va_list)arg
+{
+  [self subclassResponsibility:_cmd];
+  return 0;
+}
+
 - (int) readFormat: (id <String>)format, ...
 {
   [self subclassResponsibility:_cmd];