Index: ext/fts5/fts5_aux.c
==================================================================
--- ext/fts5/fts5_aux.c
+++ ext/fts5/fts5_aux.c
@@ -584,10 +584,11 @@
       p->aFreq = &p->aIDF[nPhrase];
     }
 
     /* Calculate the average document length for this FTS5 table */
     if( rc==SQLITE_OK ) rc = pApi->xRowCount(pFts, &nRow);
+    assert( rc!=SQLITE_OK || nRow>0 );
     if( rc==SQLITE_OK ) rc = pApi->xColumnTotalSize(pFts, -1, &nToken);
     if( rc==SQLITE_OK ) p->avgdl = (double)nToken  / (double)nRow;
 
     /* Calculate an IDF for each phrase in the query */
     for(i=0; rc==SQLITE_OK && i<nPhrase; i++){

Index: ext/fts5/fts5_storage.c
==================================================================
--- ext/fts5/fts5_storage.c
+++ ext/fts5/fts5_storage.c
@@ -1076,11 +1076,17 @@
 }
 
 int sqlite3Fts5StorageRowCount(Fts5Storage *p, i64 *pnRow){
   int rc = fts5StorageLoadTotals(p, 0);
   if( rc==SQLITE_OK ){
+    /* nTotalRow being zero does not necessarily indicate a corrupt 
+    ** database - it might be that the FTS5 table really does contain zero
+    ** rows. However this function is only called from the xRowCount() API,
+    ** and there is no way for that API to be invoked if the table contains
+    ** no rows. Hence the FTS5_CORRUPT return.  */
     *pnRow = p->nTotalRow;
+    if( p->nTotalRow<=0 ) rc = FTS5_CORRUPT;
   }
   return rc;
 }
 
 /*

Index: ext/fts5/test/fts5corrupt3.test
==================================================================
--- ext/fts5/test/fts5corrupt3.test
+++ ext/fts5/test/fts5corrupt3.test
@@ -4649,10 +4649,38 @@
 
 do_execsql_test 37.1 {
   UPDATE t1_data SET block = X'FFFFFFFF0101010001010101' WHERE rowid = 10;
   SELECT rowid FROM t1('a');
 } {1}
+
+#-------------------------------------------------------------------------
+reset_db 
+do_execsql_test 38.0 {
+  CREATE VIRTUAL TABLE t1 USING fts5(b, c);
+  INSERT INTO t1 VALUES('a', 'b');
+  INSERT INTO t1 VALUES('a', 'b');
+  SELECT quote(block) FROM t1_data WHERE rowid=1;
+} {X'020202'}
+
+do_execsql_test 38.1 {
+  SELECT * FROM t1('a b') ORDER BY rank;
+} {a b a b}
+
+do_execsql_test 38.2 {
+  UPDATE t1_data SET block = X'000202' WHERE rowid=1;
+}
+breakpoint
+do_catchsql_test 38.3 {
+  SELECT * FROM t1('a b') ORDER BY rank;
+} {1 {database disk image is malformed}}
+
+db close
+sqlite3 db test.db
+do_catchsql_test 38.4 {
+  SELECT * FROM t1('a b') ORDER BY rank;
+} {1 {database disk image is malformed}}
+
 
 
 
 sqlite3_fts5_may_be_corrupt 0
 finish_test