Index: src/pager.c
==================================================================
--- src/pager.c
+++ src/pager.c
@@ -4727,11 +4727,11 @@
 #ifdef SQLITE_ENABLE_DESERIALIZE
   int memJM = 0;           /* Memory journal mode */
 #else
 # define memJM 0
 #endif
-  int readOnly = 0;        /* True if this is a read-only file */
+  int readOnly = PAGER_READWRITE;   /* True if this is a read-only file */
   int journalFileSize;     /* Bytes to allocate for each journal fd */
   char *zPathname = 0;     /* Full path to database file */
   int nPathname = 0;       /* Number of bytes in zPathname */
   int useJournal = (flags & PAGER_OMIT_JOURNAL)==0; /* False to omit journal */
   int pcacheSize = sqlite3PcacheSize();       /* Bytes to allocate for PCache */
@@ -4858,10 +4858,11 @@
     assert( !memDb );
 #ifdef SQLITE_ENABLE_DESERIALIZE
     memJM = (fout&SQLITE_OPEN_MEMORY)!=0;
 #endif
     readOnly = (fout&SQLITE_OPEN_READONLY)!=0;
+    assert( readOnly==PAGER_READWRITE || readOnly==PAGER_READONLY );
 
     /* If the file was successfully opened for read/write access,
     ** choose a default page size in case we have to create the
     ** database file. The default page size is the maximum of:
     **
@@ -4897,10 +4898,11 @@
       }
       pPager->noLock = sqlite3_uri_boolean(zFilename, "nolock", 0);
       if( (iDc & SQLITE_IOCAP_IMMUTABLE)!=0
        || sqlite3_uri_boolean(zFilename, "immutable", 0) ){
           vfsFlags |= SQLITE_OPEN_READONLY;
+          readOnly = PAGER_IMMUTABLE;
           goto act_like_temp_file;
       }
     }
   }else{
     /* If a temporary file is requested, it is not opened immediately.
@@ -4916,11 +4918,13 @@
 act_like_temp_file:
     tempFile = 1;
     pPager->eState = PAGER_READER;     /* Pretend we already have a lock */
     pPager->eLock = EXCLUSIVE_LOCK;    /* Pretend we are in EXCLUSIVE mode */
     pPager->noLock = 1;                /* Do no locking */
-    readOnly = (vfsFlags&SQLITE_OPEN_READONLY);
+    if( (vfsFlags & SQLITE_OPEN_READONLY)!=0 && readOnly==PAGER_READWRITE ){
+      readOnly = PAGER_READONLY;
+    }
   }
 
   /* The following call to PagerSetPagesize() serves to set the value of 
   ** Pager.pageSize and to allocate the Pager.pTmpSpace buffer.
   */
@@ -6694,10 +6698,16 @@
 }
 
 /*
 ** Return TRUE if the database file is opened read-only.  Return FALSE
 ** if the database is (in theory) writable.
+**
+** Actually, the return value is one of:
+**
+**     PAGER_READWRITE  (value 0 - false)
+**     PAGER_READONLY   (value 1 - true)
+**     PAGER_IMMUTABLE  (value 2 - also true)
 */
 u8 sqlite3PagerIsreadonly(Pager *pPager){
   return pPager->readOnly;
 }
 

Index: src/pager.h
==================================================================
--- src/pager.h
+++ src/pager.h
@@ -197,10 +197,14 @@
   int sqlite3PagerWalFramesize(Pager *pPager);
 #endif
 
 /* Functions used to query pager state and configuration. */
 u8 sqlite3PagerIsreadonly(Pager*);
+/* Return values from sqlite3PagerIsreadonly() */
+#define PAGER_READWRITE  0   /* Read/write database */
+#define PAGER_READONLY   1   /* Read only but might change by outside forces */
+#define PAGER_IMMUTABLE  2   /* Guaranteed to never change */
 u32 sqlite3PagerDataVersion(Pager*);
 #ifdef SQLITE_DEBUG
   int sqlite3PagerRefcount(Pager*);
 #endif
 int sqlite3PagerMemUsed(Pager*);