Index: src/diff.c
==================================================================
--- src/diff.c
+++ src/diff.c
@@ -881,10 +881,11 @@
   int m, ma, mb;/* Number of lines to output */
   int skip;     /* Number of lines to skip */
   int nChunk = 0; /* Number of chunks of diff output seen so far */
   SbsLine s;    /* Output line buffer */
 
+  memset(&s, 0, sizeof(s));
   s.zLine = fossil_malloc( 10*width + 200 );
   if( s.zLine==0 ) return;
   s.width = width;
   s.escHtml = escHtml;
   s.iStart = -1;