diff --git a/src/mred/mred.cxx b/src/mred/mred.cxx
index d4000c9a13..1809a13fe6 100644
--- a/src/mred/mred.cxx
+++ b/src/mred/mred.cxx
@@ -2466,10 +2466,12 @@ static Bool RecordInput(void *m, wxEvent *event, void *data)
   media->Insert("\n");
   start = media->GetStartPosition();
   len = start - ioFrame->endpos;
-  s = media->GetTextUTF8(ioFrame->endpos, start);
-  ioFrame->endpos = start;
-
-  scheme_write_byte_string(s, len, stdin_pipe);
+  if (len > 0) {
+    s = media->GetTextUTF8(ioFrame->endpos, start);
+    ioFrame->endpos = start;
+    
+    scheme_write_byte_string(s, len, stdin_pipe);
+  }
 
   return TRUE;
 }