diff --git a/pkg/serializer/explorer.go b/pkg/serializer/explorer.go
index 4f94b09..be49edd 100644
--- a/pkg/serializer/explorer.go
+++ b/pkg/serializer/explorer.go
@@ -97,6 +97,7 @@ type WopiFileInfo struct {
 	// Required
 	BaseFileName string
 	Version      string
+	Size         int64
 
 	// Breadcrumb
 	BreadcrumbBrandName  string
@@ -117,6 +118,7 @@ type WopiFileInfo struct {
 	IsAnonymousUser  bool
 	UserFriendlyName string
 	UserId           string
+	OwnerId          string
 
 	// Permission
 	ReadOnly      bool
diff --git a/pkg/wopi/discovery.go b/pkg/wopi/discovery.go
index 20467b1..d4f480f 100644
--- a/pkg/wopi/discovery.go
+++ b/pkg/wopi/discovery.go
@@ -12,8 +12,9 @@ import (
 type ActonType string
 
 var (
-	ActionPreview = ActonType("embedview")
-	ActionEdit    = ActonType("edit")
+	ActionPreview         = ActonType("embedview")
+	ActionPreviewFallback = ActonType("view")
+	ActionEdit            = ActonType("edit")
 )
 
 const (
@@ -33,8 +34,9 @@ func (c *client) AvailableExts() []string {
 	for ext, actions := range c.actions {
 		_, previewable := actions[string(ActionPreview)]
 		_, editable := actions[string(ActionEdit)]
+		_, previewableFallback := actions[string(ActionPreviewFallback)]
 
-		if previewable || editable {
+		if previewable || editable || previewableFallback {
 			exts = append(exts, strings.TrimPrefix(ext, "."))
 		}
 	}
diff --git a/pkg/wopi/wopi.go b/pkg/wopi/wopi.go
index 6120cf3..bac734d 100644
--- a/pkg/wopi/wopi.go
+++ b/pkg/wopi/wopi.go
@@ -58,7 +58,7 @@ const (
 	MethodRename      = "RENAME_FILE"
 
 	wopiSrcPlaceholder    = "WOPI_SOURCE"
-	wopiSrcParamDefault   = "wopisrc"
+	wopiSrcParamDefault   = "WOPISrc"
 	sessionExpiresPadding = 10
 	wopiHeaderPrefix      = "X-WOPI-"
 )
@@ -67,6 +67,9 @@ const (
 func Init() {
 	settings := model.GetSettingByNames("wopi_endpoint", "wopi_enabled")
 	if !model.IsTrueVal(settings["wopi_enabled"]) {
+		DefaultMu.Lock()
+		Default = nil
+		DefaultMu.Unlock()
 		return
 	}
 
@@ -126,14 +129,20 @@ func (c *client) NewSession(user *model.User, file *model.File, action ActonType
 		return nil, ErrActionNotSupported
 	}
 
-	actionConfig, ok := availableActions[string(action)]
-	if !ok {
-		// Preferred action not available, fallback to view only action
-		if actionConfig, ok = availableActions[string(ActionPreview)]; !ok {
-			return nil, ErrActionNotSupported
+	var (
+		actionConfig Action
+	)
+	fallbackOrder := []ActonType{action, ActionPreview, ActionPreviewFallback, ActionEdit}
+	for _, a := range fallbackOrder {
+		if actionConfig, ok = availableActions[string(a)]; ok {
+			break
 		}
 	}
 
+	if actionConfig.Urlsrc == "" {
+		return nil, ErrActionNotSupported
+	}
+
 	// Generate WOPI REST endpoint for given file
 	baseURL := model.GetSiteURL()
 	linkPath, err := url.Parse(fmt.Sprintf("/api/v3/wopi/files/%s", hashid.HashID(file.ID, hashid.FileID)))
diff --git a/service/explorer/wopi.go b/service/explorer/wopi.go
index d959b26..9ee7c30 100644
--- a/service/explorer/wopi.go
+++ b/service/explorer/wopi.go
@@ -93,6 +93,8 @@ func (service *WopiService) FileInfo(c *gin.Context) (*serializer.WopiFileInfo,
 		IsAnonymousUser:        true,
 		ReadOnly:               true,
 		ClosePostMessage:       true,
+		Size:                   int64(fs.FileTarget[0].Size),
+		OwnerId:                hashid.HashID(fs.FileTarget[0].UserID, hashid.UserID),
 	}
 
 	if session.Action == wopi.ActionEdit {