Index: ext/fts5/fts5_aux.c
==================================================================
--- ext/fts5/fts5_aux.c
+++ ext/fts5/fts5_aux.c
@@ -355,10 +355,20 @@
     *piPos = iAdj;
   }
 
   return rc;
 }
+
+/*
+** Return the value in pVal interpreted as utf-8 text. Except, if pVal 
+** contains a NULL value, return a pointer to a static string zero
+** bytes in length instead of a NULL pointer.
+*/
+static const char *valueToText(sqlite3_value *pVal){
+  const char *zRet = (const char*)sqlite3_value_text(pVal);
+  return zRet ? zRet : "";
+}
 
 /*
 ** Implementation of snippet() function.
 */
 static void fts5SnippetFunction(
@@ -391,13 +401,13 @@
   }
 
   nCol = pApi->xColumnCount(pFts);
   memset(&ctx, 0, sizeof(HighlightContext));
   iCol = sqlite3_value_int(apVal[0]);
-  ctx.zOpen = (const char*)sqlite3_value_text(apVal[1]);
-  ctx.zClose = (const char*)sqlite3_value_text(apVal[2]);
-  zEllips = (const char*)sqlite3_value_text(apVal[3]);
+  ctx.zOpen = valueToText(apVal[1]);
+  ctx.zClose = valueToText(apVal[2]);
+  zEllips = valueToText(apVal[3]);
   nToken = sqlite3_value_int(apVal[4]);
 
   iBestCol = (iCol>=0 ? iCol : 0);
   nPhrase = pApi->xPhraseCount(pFts);
   aSeen = sqlite3_malloc(nPhrase);

Index: ext/fts5/test/fts5af.test
==================================================================
--- ext/fts5/test/fts5af.test
+++ ext/fts5/test/fts5af.test
@@ -172,9 +172,19 @@
   );
 }
 do_execsql_test 5.1 {
   SELECT snippet(p1, 0, '[', ']', '...', 6) FROM p1('x');
 } {{[x] a a a a a...}}
+
+do_execsql_test 5.2 {
+  SELECT snippet(p1, 0, '[', ']', NULL, 6) FROM p1('x');
+} {{[x] a a a a a}}
+do_execsql_test 5.3 {
+  SELECT snippet(p1, 0, NULL, ']', '...', 6) FROM p1('x');
+} {{x] a a a a a...}}
+do_execsql_test 5.4 {
+  SELECT snippet(p1, 0, '[', NULL, '...', 6) FROM p1('x');
+} {{[x a a a a a...}}
 
 } ;# foreach_detail_mode 
 
 finish_test