Index: src/btree.c
==================================================================
--- src/btree.c
+++ src/btree.c
@@ -8524,5 +8524,12 @@
 */
 void sqlite3BtreeCursorHints(BtCursor *pCsr, unsigned int mask){
   assert( mask==BTREE_BULKLOAD || mask==0 );
   pCsr->hints = mask;
 }
+
+/*
+** Return true if the given Btree is read-only.
+*/
+int sqlite3BtreeIsReadonly(Btree *p){
+  return (p->pBt->btsFlags & BTS_READ_ONLY)!=0;
+}

Index: src/btree.h
==================================================================
--- src/btree.h
+++ src/btree.h
@@ -192,10 +192,11 @@
 int sqlite3BtreePutData(BtCursor*, u32 offset, u32 amt, void*);
 void sqlite3BtreeIncrblobCursor(BtCursor *);
 void sqlite3BtreeClearCursor(BtCursor *);
 int sqlite3BtreeSetVersion(Btree *pBt, int iVersion);
 void sqlite3BtreeCursorHints(BtCursor *, unsigned int mask);
+int sqlite3BtreeIsReadonly(Btree *pBt);
 
 #ifndef NDEBUG
 int sqlite3BtreeCursorIsValid(BtCursor*);
 #endif
 

Index: src/main.c
==================================================================
--- src/main.c
+++ src/main.c
@@ -3443,7 +3443,7 @@
 ** Return 1 if database is read-only or 0 if read/write.  Return -1 if
 ** no such database exists.
 */
 int sqlite3_db_readonly(sqlite3 *db, const char *zDbName){
   Btree *pBt = sqlite3DbNameToBtree(db, zDbName);
-  return pBt ? sqlite3PagerIsreadonly(sqlite3BtreePager(pBt)) : -1;
+  return pBt ? sqlite3BtreeIsReadonly(pBt) : -1;
 }

Index: test/rdonly.test
==================================================================
--- test/rdonly.test
+++ test/rdonly.test
@@ -30,10 +30,13 @@
     CREATE TABLE t1(x);
     INSERT INTO t1 VALUES(1);
     SELECT * FROM t1;
   }
 } {1}
+do_test rdonly-1.1.1 {
+  sqlite3_db_readonly db main
+} {0}
 
 # Changes the write version from 1 to 3.  Verify that the database
 # can be read but not written.
 #
 do_test rdonly-1.2 {
@@ -45,10 +48,13 @@
   sqlite3 db test.db
   execsql {
     SELECT * FROM t1;
   }
 } {1}
+do_test rdonly-1.3.1 {
+  sqlite3_db_readonly db main
+} {1}
 do_test rdonly-1.4 {
   catchsql {
     INSERT INTO t1 VALUES(2)
   }
 } {1 {attempt to write a readonly database}}