diff --git a/watchdog/main.go b/watchdog/main.go
index 224bdbeb..387b00df 100644
--- a/watchdog/main.go
+++ b/watchdog/main.go
@@ -42,6 +42,8 @@ func debugHeaders(source *http.Header, direction string) {
 }
 
 func pipeRequest(config *WatchdogConfig, w http.ResponseWriter, r *http.Request) {
+	startTime := time.Now()
+
 	parts := strings.Split(config.faasProcess, " ")
 
 	if config.debugHeaders {
@@ -103,6 +105,9 @@ func pipeRequest(config *WatchdogConfig, w http.ResponseWriter, r *http.Request)
 		}
 	}
 
+	execTime := time.Since(startTime).Seconds()
+	w.Header().Set("X-Duration-Seconds", fmt.Sprintf("%f", execTime))
+
 	w.WriteHeader(200)
 	w.Write(out)
 
diff --git a/watchdog/requesthandler_test.go b/watchdog/requesthandler_test.go
index 7c9b03d3..87adebaa 100644
--- a/watchdog/requesthandler_test.go
+++ b/watchdog/requesthandler_test.go
@@ -20,6 +20,33 @@ func TestHandler_make(t *testing.T) {
 	}
 }
 
+func TestHandler_HasXDurationSecondsHeader(t *testing.T) {
+	rr := httptest.NewRecorder()
+
+	body := "hello"
+	req, err := http.NewRequest("POST", "/", bytes.NewBufferString(body))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	config := WatchdogConfig{
+		faasProcess: "cat",
+	}
+	handler := makeRequestHandler(&config)
+	handler(rr, req)
+
+	required := http.StatusOK
+	if status := rr.Code; status != required {
+		t.Errorf("handler returned wrong status code: got %v, but wanted %v",
+			status, required)
+	}
+
+	seconds := rr.Header().Get("X-Duration-Seconds")
+	if len(seconds) == 0 {
+		t.Errorf("Exec of cat should have given a duration as an X-Duration-Seconds header\n")
+	}
+}
+
 func TestHandler_StatusOKAllowed_ForPOST(t *testing.T) {
 	rr := httptest.NewRecorder()