diff --git a/renderer.go b/renderer.go
index a6b4118..4875745 100644
--- a/renderer.go
+++ b/renderer.go
@@ -26,6 +26,8 @@ type GlobalRenderData struct {
 
 	Title string
 
+	HavePlugin func(name string) bool
+
 	// additional plugin-specific data
 	Extra map[string]interface{}
 }
@@ -74,6 +76,15 @@ func NewBaseRenderData(ctx *Context) *BaseRenderData {
 		Path:  strings.Split(ctx.Request().URL.Path, "/")[1:],
 		Title: "Webmail",
 		URL:   ctx.Request().URL,
+
+		HavePlugin: func(name string) bool {
+			for _, plugin := range ctx.Server.plugins {
+				if plugin.Name() == name {
+					return true
+				}
+			}
+			return false
+		},
 	}
 
 	if ctx.Session != nil {
diff --git a/themes/alps/nav.html b/themes/alps/nav.html
index 1678434..d14a862 100644
--- a/themes/alps/nav.html
+++ b/themes/alps/nav.html
@@ -6,18 +6,22 @@
       class="active"
       {{ end }}
     >Email</a>
+    {{ if call .GlobalData.HavePlugin "caldav" }}
     <a
       href="/calendar"
       {{ if eq $page "calendar" }}
       class="active"
       {{ end }}
     >Calendar</a>
+    {{ end }}
+    {{ if call .GlobalData.HavePlugin "carddav" }}
     <a
       href="/contacts"
       {{ if eq $page "contacts" }}
       class="active"
       {{ end }}
     >Contacts</a>
+    {{ end }}
     <div>
       <span>{{ .GlobalData.Username }}</span>
       <a href="/settings">Settings</a>