4 files changed, 12 insertions, 5 deletions
diff --git a/src/sqlite.h.in b/src/sqlite.h.in
index 8419392cf..8e2727f6a 100644
--- a/src/sqlite.h.in
+++ b/src/sqlite.h.in
@@ -5627,7 +5627,7 @@ int sqlite3_create_module_v2(
 */
 struct sqlite3_vtab {
   const sqlite3_module *pModule;  /* The module for this virtual table */
-  int nRef;                       /* NO LONGER USED */
+  int nRef;                       /* Number of open cursors */
   char *zErrMsg;                  /* Error message from sqlite3_mprintf() */
   /* Virtual table implementations will typically add additional fields */
 };
diff --git a/src/vdbe.c b/src/vdbe.c
index bba6a90bf..82c313a2d 100644
--- a/src/vdbe.c
+++ b/src/vdbe.c
@@ -6081,6 +6081,7 @@ case OP_VOpen: {
     pCur = allocateCursor(p, pOp->p1, 0, -1, 0);
     if( pCur ){
       pCur->pVtabCursor = pVtabCursor;
+      pVtab->nRef++;
     }else{
       db->mallocFailed = 1;
       pModule->xClose(pVtabCursor);
diff --git a/src/vdbeaux.c b/src/vdbeaux.c
index 8397fbc10..bd00786eb 100644
--- a/src/vdbeaux.c
+++ b/src/vdbeaux.c
@@ -1782,6 +1782,8 @@ void sqlite3VdbeFreeCursor(Vdbe *p, VdbeCursor *pCx){
   else if( pCx->pVtabCursor ){
     sqlite3_vtab_cursor *pVtabCursor = pCx->pVtabCursor;
     const sqlite3_module *pModule = pVtabCursor->pVtab->pModule;
+    assert( pVtabCursor->pVtab->nRef>0 );
+    pVtabCursor->pVtab->nRef--;
     pModule->xClose(pVtabCursor);
   }
 #endif
diff --git a/src/vtab.c b/src/vtab.c
index 4631a7d0d..23f49bafc 100644
--- a/src/vtab.c
+++ b/src/vtab.c
@@ -780,11 +780,15 @@ int sqlite3VtabCallDestroy(sqlite3 *db, int iDb, const char *zTab){
 
   pTab = sqlite3FindTable(db, zTab, db->aDb[iDb].zName);
   if( ALWAYS(pTab!=0 && pTab->pVTable!=0) ){
-    VTable *p = vtabDisconnectAll(db, pTab);
-
-    assert( rc==SQLITE_OK );
+    VTable *p;
+    for(p=pTab->pVTable; p; p=p->pNext){
+      assert( p->pVtab );
+      if( p->pVtab->nRef>0 ){
+        return SQLITE_LOCKED;
+      }
+    }
+    p = vtabDisconnectAll(db, pTab);
     rc = p->pMod->pModule->xDestroy(p->pVtab);
-
     /* Remove the sqlite3_vtab* from the aVTrans[] array, if applicable */
     if( rc==SQLITE_OK ){
       assert( pTab->pVTable==p && p->pNext==0 );