diff --git a/server/router/router.go b/server/router/router.go
index d7ee836..f1378ee 100644
--- a/server/router/router.go
+++ b/server/router/router.go
@@ -6,6 +6,7 @@ package router
 import (
 	"fmt"
 	"net/http"
+	"path"
 	"strings"
 
 	"github.com/goburrow/melon/server/filter"
@@ -88,7 +89,11 @@ func (h *Router) Endpoints() []string {
 // which should include ServeMux as the last one.
 func (h *Router) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	if h.pathPrefix != "" {
-		r.URL.Path = strings.TrimPrefix(r.URL.Path, h.pathPrefix)
+		p := strings.TrimPrefix(r.URL.Path, h.pathPrefix)
+		if p == "" {
+			p = "/"
+		}
+		r.URL.Path = p
 	}
 	h.filterChain.ServeHTTP(w, r)
 }
@@ -103,7 +108,16 @@ func (h *Router) AddFilter(f filter.Filter) {
 type Option func(r *Router)
 
 // WithPathPrefix returns an Option which sets path prefix for Router.
+// If there is no leading slash, it will be added to prefix.
 func WithPathPrefix(prefix string) Option {
+	prefix = strings.TrimSpace(prefix)
+	if prefix != "" {
+		// Clean and add leading slash if necessary
+		prefix = path.Clean(prefix)
+		if prefix[0] != '/' {
+			prefix = "/" + prefix
+		}
+	}
 	return func(r *Router) {
 		r.pathPrefix = prefix
 	}
diff --git a/server/router/router_test.go b/server/router/router_test.go
index 9904e68..3791731 100644
--- a/server/router/router_test.go
+++ b/server/router/router_test.go
@@ -1,5 +1,28 @@
 package router
 
-import "github.com/goburrow/melon/core"
+import (
+	"net/http"
+	"testing"
+
+	"github.com/goburrow/melon/core"
+)
 
 var _ core.Router = (*Router)(nil)
+var _ http.Handler = (*Router)(nil)
+
+func TestPathPrefix(t *testing.T) {
+	tests := map[string]string{
+		"":          "",
+		"/abc/def":  "/abc/def",
+		"/a/b//c//": "/a/b/c",
+		"a//b/":     "/a/b",
+		".":         "/.",
+		"/":         "/",
+	}
+	for k, v := range tests {
+		r := New(WithPathPrefix(k))
+		if v != r.pathPrefix {
+			t.Errorf("unexpected path prefix: %v, want: %v", r.pathPrefix, v)
+		}
+	}
+}