diff --git a/mem.go b/mem.go
index 9cf76a5..7fb6fa2 100644
--- a/mem.go
+++ b/mem.go
@@ -88,6 +88,22 @@ func (m memory) writeUint64(ptr uint32, v uint64) {
 	}
 }
 
+func (m memory) readBool8(ptr uint32) bool {
+	v := m.readUint8(ptr)
+	if v != 0 {
+		return true
+	}
+	return false
+}
+
+func (m memory) writeBool8(ptr uint32, v bool) {
+	var b uint8
+	if v {
+		b = 1
+	}
+	m.writeUint8(ptr, b)
+}
+
 func (m memory) readFloat64(ptr uint32) float64 {
 	return math.Float64frombits(m.readUint64(ptr))
 }
diff --git a/sqlite3/os.c b/sqlite3/os.c
index c66f970..e76b498 100644
--- a/sqlite3/os.c
+++ b/sqlite3/os.c
@@ -21,6 +21,7 @@ struct os_file {
   char lock;
   char psow;
   char syncDir;
+  char readOnly;
   int lockTimeout;
 };
 
@@ -28,6 +29,7 @@ static_assert(offsetof(struct os_file, id) == 4, "Unexpected offset");
 static_assert(offsetof(struct os_file, lock) == 8, "Unexpected offset");
 static_assert(offsetof(struct os_file, psow) == 9, "Unexpected offset");
 static_assert(offsetof(struct os_file, syncDir) == 10, "Unexpected offset");
+static_assert(offsetof(struct os_file, readOnly) == 11, "Unexpected offset");
 static_assert(offsetof(struct os_file, lockTimeout) == 12, "Unexpected offset");
 
 int os_close(sqlite3_file *);
diff --git a/vfs.go b/vfs.go
index 0e445c4..de0ff6c 100644
--- a/vfs.go
+++ b/vfs.go
@@ -236,6 +236,9 @@ func vfsOpen(ctx context.Context, mod api.Module, pVfs, zName, pFile uint32, fla
 
 	vfsFile.Open(ctx, mod, pFile, file)
 
+	if flags&OPEN_READONLY != 0 {
+		vfsFile.SetReadOnly(ctx, mod, pFile, true)
+	}
 	if runtime.GOOS != "windows" &&
 		flags&(OPEN_CREATE) != 0 &&
 		flags&(OPEN_MAIN_JOURNAL|OPEN_SUPER_JOURNAL|OPEN_WAL) != 0 {
diff --git a/vfs_file.go b/vfs_file.go
index e400b50..70f02be 100644
--- a/vfs_file.go
+++ b/vfs_file.go
@@ -13,6 +13,7 @@ const (
 	vfsFileIDOffset          = 4
 	vfsFileLockOffset        = 8
 	vfsFileSyncDirOffset     = 10
+	vfsFileReadOnlyOffset    = 11
 	vfsFileLockTimeoutOffset = 12
 )
 
@@ -71,17 +72,20 @@ func (vfsFileMethods) GetLockTimeout(ctx context.Context, mod api.Module, pFile
 
 func (vfsFileMethods) GetSyncDir(ctx context.Context, mod api.Module, pFile uint32) bool {
 	mem := memory{mod}
-	if b := mem.readUint8(pFile + vfsFileSyncDirOffset); b != 0 {
-		return true
-	}
-	return false
+	return mem.readBool8(pFile + vfsFileSyncDirOffset)
 }
 
-func (vfsFileMethods) SetSyncDir(ctx context.Context, mod api.Module, pFile uint32, state bool) {
+func (vfsFileMethods) SetSyncDir(ctx context.Context, mod api.Module, pFile uint32, val bool) {
 	mem := memory{mod}
-	var b uint8
-	if state {
-		b = 1
-	}
-	mem.writeUint8(pFile+vfsFileSyncDirOffset, b)
+	mem.writeBool8(pFile+vfsFileSyncDirOffset, val)
+}
+
+func (vfsFileMethods) GetReadOnly(ctx context.Context, mod api.Module, pFile uint32) bool {
+	mem := memory{mod}
+	return mem.readBool8(pFile + vfsFileReadOnlyOffset)
+}
+
+func (vfsFileMethods) SetReadOnly(ctx context.Context, mod api.Module, pFile uint32, val bool) {
+	mem := memory{mod}
+	mem.writeBool8(pFile+vfsFileReadOnlyOffset, val)
 }
diff --git a/vfs_lock.go b/vfs_lock.go
index a67cb92..4ccd3a3 100644
--- a/vfs_lock.go
+++ b/vfs_lock.go
@@ -65,6 +65,7 @@ func vfsLock(ctx context.Context, mod api.Module, pFile uint32, eLock vfsLockSta
 	file := vfsFile.GetOS(ctx, mod, pFile)
 	cLock := vfsFile.GetLock(ctx, mod, pFile)
 	timeout := vfsFile.GetLockTimeout(ctx, mod, pFile)
+	readOnly := vfsFile.GetReadOnly(ctx, mod, pFile)
 
 	switch {
 	case cLock < _NO_LOCK || cLock > _EXCLUSIVE_LOCK:
@@ -83,6 +84,11 @@ func vfsLock(ctx context.Context, mod api.Module, pFile uint32, eLock vfsLockSta
 		return _OK
 	}
 
+	// Do not allow any kind of write-lock on a read-only database.
+	if readOnly && eLock > _RESERVED_LOCK {
+		return uint32(IOERR_LOCK)
+	}
+
 	switch eLock {
 	case _SHARED_LOCK:
 		// Must be unlocked to get SHARED.