Index: src/os_unix.c
==================================================================
--- src/os_unix.c
+++ src/os_unix.c
@@ -4877,11 +4877,13 @@
 static void unixShmBarrier(
   sqlite3_file *fd                /* Database file holding the shared memory */
 ){
   UNUSED_PARAMETER(fd);
   sqlite3MemoryBarrier();         /* compiler-defined memory barrier */
-  assert( unixFileMutexNotheld((unixFile*)fd) );
+  assert( fd->pMethods->xLock==nolockLock 
+       || unixFileMutexNotheld((unixFile*)fd) 
+  );
   unixEnterMutex();               /* Also mutex, for redundancy */
   unixLeaveMutex();
 }
 
 /*