diff --git a/stream/filters/pure_filter.hpp b/stream/filters/pure_filter.hpp
index ed1690d8c..f0ce91f87 100644
--- a/stream/filters/pure_filter.hpp
+++ b/stream/filters/pure_filter.hpp
@@ -31,6 +31,7 @@ class PureFilter : public Stream
 
   size_t read(void *buf, size_t count) { return src->read(buf, count); }
   size_t write(const void *buf, size_t count) { return src->write(buf,count); }
+  void flush() { src->flush(); }
   void seek(size_t pos) { src->seek(pos); }
   size_t tell() const { return src->tell(); }
   size_t size() const { return src->size(); }
diff --git a/stream/filters/slice_stream.hpp b/stream/filters/slice_stream.hpp
index 20f202bdc..6337b9d57 100644
--- a/stream/filters/slice_stream.hpp
+++ b/stream/filters/slice_stream.hpp
@@ -72,6 +72,7 @@ class SliceStream : public Stream
   bool eof() const { return pos == length; }
   size_t tell() const { return pos; }
   size_t size() const { return length; }
+  void flush() { src->flush(); }
 
   const void *getPtr() { return getPtr(0, length); }
   const void *getPtr(size_t size)
diff --git a/stream/servers/std_ostream.hpp b/stream/servers/std_ostream.hpp
index 32999e8c1..9ec6609e9 100644
--- a/stream/servers/std_ostream.hpp
+++ b/stream/servers/std_ostream.hpp
@@ -37,13 +37,16 @@ class StdOStream : public Stream
     inf->write((const char*)buf, len);
     if(inf->fail())
       fail("error writing to stream");
-
-    // Unfortunately, stupid std::ostream doesn't have a pcount() to
-    // match gcount() for input. In general the std::iostream system
-    // is an idiotically designed stream library.
+    // Just return len, but that is ok. The only cases where we would
+    // return less than len is when an error occured.
     return len;
   }
 
+  void flush()
+  {
+    inf->flush();
+  }
+
   void seek(size_t pos)
   {
     inf->seekp(pos);
diff --git a/stream/stream.hpp b/stream/stream.hpp
index bc369f6cd..aa9c14a9e 100644
--- a/stream/stream.hpp
+++ b/stream/stream.hpp
@@ -52,6 +52,9 @@ class Stream
   */
   virtual size_t write(const void *buf, size_t count) { assert(0); return 0; }
 
+  /// Flush an output stream. Does nothing for non-writing streams.
+  virtual void flush() {}
+
   /// Seek to an absolute position in this stream. Not all streams are
   /// seekable.
   virtual void seek(size_t pos) = 0;