diff --git a/src/StreamBuffer.cc b/src/StreamBuffer.cc
index 77bf747..fa970e5 100644
--- a/src/StreamBuffer.cc
+++ b/src/StreamBuffer.cc
@@ -273,9 +273,18 @@ StreamBuffer StreamBuffer::expand(long start, long length) const
     if (start < 0)
     {
         start += len;
-        if (start < 0) start = 0;
     }
-    end = length >= 0 ? start+length : len;
+    if (length < 0)
+    {
+        start += length;
+        length = -length;
+    }
+    if (start < 0)
+    {
+        length += start;
+        start = 0;
+    }
+    end = start+length;
     if (end > len) end = len;
     StreamBuffer result((end-start)*2);
     start += offs;
diff --git a/src/StreamBuffer.h b/src/StreamBuffer.h
index 563830b..9bf8585 100644
--- a/src/StreamBuffer.h
+++ b/src/StreamBuffer.h
@@ -218,7 +218,10 @@ public:
 
 // expand: create copy of StreamBuffer where all nonprintable characters
 // are replaced by <xx> with xx being the hex code of the characters
-    StreamBuffer expand(long start=0, long length=-1) const;
+    StreamBuffer expand(long start, long length) const;
+    
+    StreamBuffer expand(long start=0) const
+        {return expand(start, len);}
 
 // dump: debug function, like expand but also show the 'hidden' memory
 // before and after the real data. Uses colours.