Index: src/alter.c
==================================================================
--- src/alter.c
+++ src/alter.c
@@ -29,13 +29,12 @@
 ** Or, if zName is not a system table, zero is returned.
 */
 static int isAlterableTable(Parse *pParse, Table *pTab){
   if( 0==sqlite3StrNICmp(pTab->zName, "sqlite_", 7) 
 #ifndef SQLITE_OMIT_VIRTUALTABLE
-   || ( (pTab->tabFlags & TF_Shadow) 
-     && (pParse->db->flags & SQLITE_Defensive)
-     && pParse->db->nVdbeExec==0
+   || ( (pTab->tabFlags & TF_Shadow)!=0
+        && sqlite3ReadOnlyShadowTables(pParse->db)
    )
 #endif
   ){
     sqlite3ErrorMsg(pParse, "table %s may not be altered", pTab->zName);
     return 1;

Index: src/build.c
==================================================================
--- src/build.c
+++ src/build.c
@@ -854,17 +854,18 @@
         sqlite3ErrorMsg(pParse, ""); /* corruptSchema() will supply the error */
         return SQLITE_ERROR;
       }
     }
   }else{
-    if( pParse->nested==0 
-     && 0==sqlite3StrNICmp(zName, "sqlite_", 7)
+    if( (pParse->nested==0 && 0==sqlite3StrNICmp(zName, "sqlite_", 7))
+     || (sqlite3ReadOnlyShadowTables(db) && sqlite3ShadowTableName(db, zName))
     ){
       sqlite3ErrorMsg(pParse, "object name reserved for internal use: %s",
                       zName);
       return SQLITE_ERROR;
     }
+
   }
   return SQLITE_OK;
 }
 
 /*
@@ -2127,11 +2128,11 @@
 ** connection.
 **
 ** zName is temporarily modified while this routine is running, but is
 ** restored to its original value prior to this routine returning.
 */
-static int isShadowTableName(sqlite3 *db, char *zName){
+int sqlite3ShadowTableName(sqlite3 *db, const char *zName){
   char *zTail;                  /* Pointer to the last "_" in zName */
   Table *pTab;                  /* Table that zName is a shadow of */
   Module *pMod;                 /* Module for the virtual table */
 
   zTail = strrchr(zName, '_');
@@ -2145,12 +2146,10 @@
   if( pMod==0 ) return 0;
   if( pMod->pModule->iVersion<3 ) return 0;
   if( pMod->pModule->xShadowName==0 ) return 0;
   return pMod->pModule->xShadowName(zTail+1);
 }
-#else
-# define isShadowTableName(x,y) 0
 #endif /* ifndef SQLITE_OMIT_VIRTUALTABLE */
 
 /*
 ** This routine is called to report the final ")" that terminates
 ** a CREATE TABLE statement.
@@ -2188,11 +2187,11 @@
   }
   assert( !db->mallocFailed );
   p = pParse->pNewTable;
   if( p==0 ) return;
 
-  if( pSelect==0 && isShadowTableName(db, p->zName) ){
+  if( pSelect==0 && sqlite3ShadowTableName(db, p->zName) ){
     p->tabFlags |= TF_Shadow;
   }
 
   /* If the db->init.busy is 1 it means we are reading the SQL off the
   ** "sqlite_master" or "sqlite_temp_master" table on the disk.
@@ -2891,23 +2890,38 @@
   }
   sqlite3VdbeAddOp4(v, OP_DropTable, iDb, 0, 0, pTab->zName, 0);
   sqlite3ChangeCookie(pParse, iDb);
   sqliteViewResetAll(db, iDb);
 }
+
+/*
+** Return TRUE if shadow tables should be read-only in the current
+** context.
+*/
+int sqlite3ReadOnlyShadowTables(sqlite3 *db){
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  if( (db->flags & SQLITE_Defensive)!=0
+   && db->pVtabCtx==0
+   && db->nVdbeExec==0
+  ){
+    return 1;
+  }
+#endif
+  return 0;
+}
 
 /*
 ** Return true if it is not allowed to drop the given table
 */
-static int tableMayNotBeDropped(Parse *pParse, Table *pTab){
+static int tableMayNotBeDropped(sqlite3 *db, Table *pTab){
   if( sqlite3StrNICmp(pTab->zName, "sqlite_", 7)==0 ){
     if( sqlite3StrNICmp(pTab->zName+7, "stat", 4)==0 ) return 0;
     if( sqlite3StrNICmp(pTab->zName+7, "parameters", 10)==0 ) return 0;
     return 1;
   }
-  if( pTab->tabFlags & TF_Shadow ){
-    sqlite3 *db = pParse->db;
-    if( (db->flags & SQLITE_Defensive)!=0 && db->nVdbeExec==0 ) return 1;
+  if( (pTab->tabFlags & TF_Shadow)!=0 && sqlite3ReadOnlyShadowTables(db) ){
+    return 1;
   }
   return 0;
 }
 
 /*
@@ -2977,11 +2991,11 @@
     if( sqlite3AuthCheck(pParse, SQLITE_DELETE, pTab->zName, 0, zDb) ){
       goto exit_drop_table;
     }
   }
 #endif
-  if( tableMayNotBeDropped(pParse, pTab) ){
+  if( tableMayNotBeDropped(db, pTab) ){
     sqlite3ErrorMsg(pParse, "table %s may not be dropped", pTab->zName);
     goto exit_drop_table;
   }
 
 #ifndef SQLITE_OMIT_VIEW

Index: src/delete.c
==================================================================
--- src/delete.c
+++ src/delete.c
@@ -68,15 +68,11 @@
   db = pParse->db;
   if( (pTab->tabFlags & TF_Readonly)!=0 ){
     return sqlite3WritableSchema(db)==0 && pParse->nested==0;
   }
   assert( pTab->tabFlags & TF_Shadow );
-  return (db->flags & SQLITE_Defensive)!=0 
-#ifndef SQLITE_OMIT_VIRTUALTABLE
-          && db->pVtabCtx==0
-#endif
-          && db->nVdbeExec==0;
+  return sqlite3ReadOnlyShadowTables(db);
 }
 
 /*
 ** Check to make sure the given table is writable.  If it is not
 ** writable, generate an error message and return 1.  If it is

Index: src/sqliteInt.h
==================================================================
--- src/sqliteInt.h
+++ src/sqliteInt.h
@@ -4544,10 +4544,16 @@
      const sqlite3_module*,
      void*,
      void(*)(void*)
    );
 #  define sqlite3VtabInSync(db) ((db)->nVTrans>0 && (db)->aVTrans==0)
+#endif
+int sqlite3ReadOnlyShadowTables(sqlite3 *db);
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  int sqlite3ShadowTableName(sqlite3 *db, const char *zName);
+#else
+# define sqlite3ShadowTableName(A,B) 0
 #endif
 int sqlite3VtabEponymousTableInit(Parse*,Module*);
 void sqlite3VtabEponymousTableClear(sqlite3*,Module*);
 void sqlite3VtabMakeWritable(Parse*,Table*);
 void sqlite3VtabBeginParse(Parse*, Token*, Token*, Token*, int);

Index: test/altertab.test
==================================================================
--- test/altertab.test
+++ test/altertab.test
@@ -544,17 +544,33 @@
 
   do_catchsql_test 16.10 {
     INSERT INTO y1_segments VALUES(1, X'1234567890');
   } {1 {table y1_segments may not be modified}}
 
+  do_catchsql_test 16.20 {
+    DROP TABLE y1_segments;
+  } {1 {table y1_segments may not be dropped}}
+
   do_catchsql_test 16.20 {
     ALTER TABLE y1_segments RENAME TO abc;
   } {1 {table y1_segments may not be altered}}
-
-  do_catchsql_test 16.21 {
-    DROP TABLE y1_segments;
-  } {1 {table y1_segments may not be dropped}}
+  sqlite3_db_config db DEFENSIVE 0
+  do_catchsql_test 16.22 {
+    ALTER TABLE y1_segments RENAME TO abc;
+  } {0 {}}
+  sqlite3_db_config db DEFENSIVE 1
+  do_catchsql_test 16.23 {
+    CREATE TABLE y1_segments AS SELECT * FROM abc;
+  } {1 {object name reserved for internal use: y1_segments}}
+  do_catchsql_test 16.24 {
+    CREATE VIEW y1_segments AS SELECT * FROM abc;
+  } {1 {object name reserved for internal use: y1_segments}}
+  sqlite3_db_config db DEFENSIVE 0
+  do_catchsql_test 16.25 {
+    ALTER TABLE abc RENAME TO y1_segments;
+  } {0 {}}
+  sqlite3_db_config db DEFENSIVE 1
 
   do_execsql_test 16.30 {
     ALTER TABLE y1 RENAME TO z1;
   }