diff --git a/api/api_bridge.go b/api/api_bridge.go
index 905c201..c1385ca 100644
--- a/api/api_bridge.go
+++ b/api/api_bridge.go
@@ -161,7 +161,7 @@ func callAPI(ebr *EndpointBridgeRequest) (record.Record, error) {
 	}
 
 	response := &EndpointBridgeResponse{
-		MimeType: w.Result().Header.Get("Content-Type"),
+		MimeType: w.Header().Get("Content-Type"),
 		Body:     w.Body.String(),
 	}
 	response.SetKey(apiDatabaseName + ":" + ebr.Path)
diff --git a/api/endpoints.go b/api/endpoints.go
index c02b9d0..7934dcd 100644
--- a/api/endpoints.go
+++ b/api/endpoints.go
@@ -15,16 +15,18 @@ import (
 
 	"github.com/safing/portbase/database/record"
 	"github.com/safing/portbase/log"
+	"github.com/safing/portbase/modules"
 )
 
 // Endpoint describes an API Endpoint.
 // Path and at least one permission are required.
 // As is exactly one function.
 type Endpoint struct {
-	Path     string
-	MimeType string
-	Read     Permission
-	Write    Permission
+	Path      string
+	MimeType  string
+	Read      Permission
+	Write     Permission
+	BelongsTo *modules.Module
 
 	// ActionFunc is for simple actions with a return message for the user.
 	ActionFunc ActionFunc `json:"-"`
@@ -268,6 +270,12 @@ func (e *Endpoint) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	// Wait for the owning module to be ready.
+	if !moduleIsReady(e.BelongsTo) {
+		http.Error(w, "The API endpoint not ready yet. Please try again later.", http.StatusServiceUnavailable)
+		return
+	}
+
 	switch r.Method {
 	case http.MethodHead:
 		w.WriteHeader(http.StatusOK)
diff --git a/api/modules.go b/api/modules.go
new file mode 100644
index 0000000..94b7594
--- /dev/null
+++ b/api/modules.go
@@ -0,0 +1,48 @@
+package api
+
+import (
+	"time"
+
+	"github.com/safing/portbase/modules"
+)
+
+type ModuleHandler interface {
+	BelongsTo() *modules.Module
+}
+
+const (
+	moduleCheckMaxWait      = 10 * time.Second
+	moduleCheckTickDuration = 500 * time.Millisecond
+)
+
+// moduleIsReady checks if the given module is online and http requests can be
+// sent its way. If the module is not online already, it will wait for a short
+// duration for it to come online.
+func moduleIsReady(m *modules.Module) (ok bool) {
+	// Check if we are given a module.
+	if m == nil {
+		// If no module is given, we assume that the handler has not been linked to
+		// a module, and we can safely continue with the request.
+		return true
+	}
+
+	// Check if the module is online.
+	if m.Online() {
+		return true
+	}
+
+	// Check if the module will come online.
+	if m.OnlineSoon() {
+		var i time.Duration
+		for i = 0; i < moduleCheckMaxWait; i += moduleCheckTickDuration {
+			// Wait a little.
+			time.Sleep(moduleCheckTickDuration)
+			// Check if module is now online.
+			if m.Online() {
+				return true
+			}
+		}
+	}
+
+	return false
+}
diff --git a/api/router.go b/api/router.go
index 5bde7b0..6fbcacd 100644
--- a/api/router.go
+++ b/api/router.go
@@ -86,12 +86,12 @@ func (mh *mainHandler) handle(w http.ResponseWriter, r *http.Request) error {
 	r = r.WithContext(ctx)
 	lrw := NewLoggingResponseWriter(w, r)
 
-	tracer.Tracef("api request: %s ___ %s", r.RemoteAddr, r.RequestURI)
+	tracer.Tracef("api request: %s ___ %s %s", r.RemoteAddr, lrw.Request.Method, r.RequestURI)
 	defer func() {
 		// Log request status.
 		if lrw.Status != 0 {
 			// If lrw.Status is 0, the request may have been hijacked.
-			tracer.Debugf("api request: %s %d %s", lrw.Request.RemoteAddr, lrw.Status, lrw.Request.RequestURI)
+			tracer.Debugf("api request: %s %d %s %s", lrw.Request.RemoteAddr, lrw.Status, lrw.Request.Method, lrw.Request.RequestURI)
 		}
 		tracer.Submit()
 	}()
@@ -130,6 +130,14 @@ func (mh *mainHandler) handle(w http.ResponseWriter, r *http.Request) error {
 		return nil
 	}
 
+	// Wait for the owning module to be ready.
+	if moduleHandler, ok := handler.(ModuleHandler); ok {
+		if !moduleIsReady(moduleHandler.BelongsTo()) {
+			http.Error(lrw, "The API endpoint not ready yet. Please try again later.", http.StatusServiceUnavailable)
+			return nil
+		}
+	}
+
 	// Add security headers.
 	if !devMode() {
 		w.Header().Set(
diff --git a/metrics/api.go b/metrics/api.go
index e206416..bbf4335 100644
--- a/metrics/api.go
+++ b/metrics/api.go
@@ -19,9 +19,10 @@ func registerAPI() error {
 	api.RegisterHandler("/metrics", &metricsAPI{})
 
 	return api.RegisterEndpoint(api.Endpoint{
-		Path:     "metrics/list",
-		Read:     api.PermitAnyone,
-		MimeType: api.MimeTypeJSON,
+		Path:      "metrics/list",
+		Read:      api.PermitAnyone,
+		MimeType:  api.MimeTypeJSON,
+		BelongsTo: module,
 		DataFunc: func(*api.Request) ([]byte, error) {
 			registryLock.RLock()
 			defer registryLock.RUnlock()