Index: src/os_unix.c
==================================================================
--- src/os_unix.c
+++ src/os_unix.c
@@ -3150,10 +3150,12 @@
   sqlite3_int64 offset
 ){
   unixFile *pFile = (unixFile *)id;
   int got;
   assert( id );
+  assert( offset>=0 );
+  assert( amt>0 );
 
   /* If this is a database file (not a journal, master-journal or temp
   ** file), the bytes in the locking range should never be read or written. */
 #if 0
   assert( pFile->pUnused==0

Index: src/os_win.c
==================================================================
--- src/os_win.c
+++ src/os_win.c
@@ -2155,10 +2155,11 @@
   DWORD nRead;                    /* Number of bytes actually read from file */
   int nRetry = 0;                 /* Number of retrys */
 
   assert( id!=0 );
   assert( amt>0 );
+  assert( offset>=0 );
   SimulateIOError(return SQLITE_IOERR_READ);
   OSTRACE(("READ file=%p, buffer=%p, amount=%d, offset=%lld, lock=%d\n",
            pFile->h, pBuf, amt, offset, pFile->locktype));
 
 #if SQLITE_MAX_MMAP_SIZE>0