1 files changed, 2 insertions, 0 deletions
diff --git a/src/where.c b/src/where.c
index 5cb52b8ad..127525006 100644
--- a/src/where.c
+++ b/src/where.c
@@ -1104,6 +1104,8 @@ static SQLITE_NOINLINE void constructAutomaticIndex(
   }
 
   /* Construct the Index object to describe this index */
+  assert( nKeyCol <= pTable->nCol + MAX(0, pTable->nCol - BMS + 1) );
+  /* ^-- This guarantees that the number of index columns will fit in the u16 */
   pIdx = sqlite3AllocateIndexObject(pParse->db, nKeyCol+HasRowid(pTable),
                                     0, &zNotUsed);
   if( pIdx==0 ) goto end_auto_index_create;