Index: src/test_devsym.c
==================================================================
--- src/test_devsym.c
+++ src/test_devsym.c
@@ -344,12 +344,16 @@
     devsym_vfs.szOsFile += g.pVfs->szOsFile;
     sqlite3_vfs_register(&devsym_vfs, 0);
   }
   if( iDeviceChar>=0 ){
     g.iDeviceChar = iDeviceChar;
+  }else{
+    g.iDeviceChar = 0;
   }
   if( iSectorSize>=0 ){
     g.iSectorSize = iSectorSize;
+  }else{
+    g.iSectorSize = 512;
   }
 }
 
 #endif