diff --git a/Source/Stream.m b/Source/Stream.m
index 96402fea6..3d1ffc96f 100644
--- a/Source/Stream.m
+++ b/Source/Stream.m
@@ -99,12 +99,17 @@
 
 - (void) flushStream
 {
-  [self subclassResponsibility:_cmd];
+  /* Do nothing. */
 }
 
 - (void) closeStream
 {
-  [self subclassResponsibility:_cmd];
+  /* Do nothing. */
+}
+
+- (BOOL) isClosed
+{
+  return NO;
 }
 
 - (void) setStreamPosition: (unsigned)i