diff --git a/cert.go b/cert.go
index a19a2bf..4f11fe6 100644
--- a/cert.go
+++ b/cert.go
@@ -8,6 +8,7 @@ import (
 	"crypto/x509"
 	"math/big"
 	"net"
+	"path"
 	"path/filepath"
 	"strings"
 	"time"
@@ -70,6 +71,27 @@ func (c *CertificateStore) Load(path string) error {
 	return nil
 }
 
+type ClientCertificateStore struct {
+	CertificateStore
+}
+
+func (c *ClientCertificateStore) Lookup(hostname, urlPath string) (*tls.Certificate, error) {
+	urlPath = path.Clean(urlPath)
+	for {
+		cert, err := c.CertificateStore.Lookup(hostname + urlPath)
+		switch err {
+		case ErrCertificateExpired, nil:
+			return cert, err
+		}
+		slash := urlPath == "/"
+		urlPath = path.Dir(urlPath)
+		if slash && urlPath == "/" {
+			break
+		}
+	}
+	return nil, ErrCertificateUnknown
+}
+
 // NewCertificate creates and returns a new parsed certificate.
 func NewCertificate(host string, duration time.Duration) (tls.Certificate, error) {
 	crt, priv, err := newX509KeyPair(host, duration)
@@ -114,12 +136,14 @@ func newX509KeyPair(host string, duration time.Duration) (*x509.Certificate, cry
 		BasicConstraintsValid: true,
 	}
 
-	hosts := strings.Split(host, ",")
-	for _, h := range hosts {
-		if ip := net.ParseIP(h); ip != nil {
-			template.IPAddresses = append(template.IPAddresses, ip)
-		} else {
-			template.DNSNames = append(template.DNSNames, h)
+	if host != "" {
+		hosts := strings.Split(host, ",")
+		for _, h := range hosts {
+			if ip := net.ParseIP(h); ip != nil {
+				template.IPAddresses = append(template.IPAddresses, ip)
+			} else {
+				template.DNSNames = append(template.DNSNames, h)
+			}
 		}
 	}
 
diff --git a/client.go b/client.go
index d8d88ae..91402b1 100644
--- a/client.go
+++ b/client.go
@@ -16,7 +16,7 @@ type Client struct {
 	// CertificateStore maps hostnames to certificates.
 	// It is used to determine which certificate to use when the server requests
 	// a certificate.
-	CertificateStore CertificateStore
+	CertificateStore ClientCertificateStore
 
 	// CheckRedirect, if not nil, will be called to determine whether
 	// to follow a redirect.
@@ -28,7 +28,7 @@ type Client struct {
 	// The returned certificate will be used when sending the request again.
 	// If the certificate is nil, the request will not be sent again and
 	// the response will be returned.
-	GetCertificate func(hostname string, store *CertificateStore) *tls.Certificate
+	GetCertificate func(req *Request, store *ClientCertificateStore) *tls.Certificate
 
 	// TrustCertificate, if not nil, will be called to determine whether the
 	// client should trust the given certificate.
@@ -61,7 +61,7 @@ func (c *Client) do(req *Request, via []*Request) (*Response, error) {
 				return req.Certificate, nil
 			}
 			// If we have already stored the certificate, return it
-			if cert, err := c.CertificateStore.Lookup(hostname(req.Host)); err == nil {
+			if cert, err := c.CertificateStore.Lookup(hostname(req.Host), req.URL.Path); err == nil {
 				return cert, nil
 			}
 			return &tls.Certificate{}, nil
@@ -111,7 +111,7 @@ func (c *Client) do(req *Request, via []*Request) (*Response, error) {
 			return resp, nil
 		}
 		if c.GetCertificate != nil {
-			if cert := c.GetCertificate(hostname(req.Host), &c.CertificateStore); cert != nil {
+			if cert := c.GetCertificate(req, &c.CertificateStore); cert != nil {
 				req.Certificate = cert
 				return c.Do(req)
 			}
diff --git a/examples/client.go b/examples/client.go
index 5180f5c..e2e1669 100644
--- a/examples/client.go
+++ b/examples/client.go
@@ -8,7 +8,6 @@ import (
 	"crypto/x509"
 	"fmt"
 	"io/ioutil"
-	"net/url"
 	"os"
 	"time"
 
@@ -47,22 +46,27 @@ func init() {
 		}
 		return err
 	}
-	client.GetCertificate = func(hostname string, store *gemini.CertificateStore) *tls.Certificate {
+	client.GetCertificate = func(req *gemini.Request, store *gemini.ClientCertificateStore) *tls.Certificate {
 		// If the certificate is in the store, return it
-		if cert, err := store.Lookup(hostname); err == nil {
+		if cert, err := store.Lookup(req.URL.Hostname(), req.URL.Path); err == nil {
 			return cert
 		}
 		// Otherwise, generate a certificate
-		fmt.Println("Generating client certificate for", hostname)
+		fmt.Println("Generating client certificate for", req.URL.Hostname()+req.URL.Path)
 		duration := time.Hour
-		cert, err := gemini.NewCertificate(hostname, duration)
+		cert, err := gemini.NewCertificate("", duration)
 		if err != nil {
 			return nil
 		}
 		// Store and return the certificate
-		store.Add(hostname, cert)
+		store.Add(req.URL.Hostname()+req.URL.Path, cert)
 		return &cert
 	}
+	client.GetInput = func(prompt string, sensitive bool) (string, bool) {
+		fmt.Printf("%s: ", prompt)
+		scanner.Scan()
+		return scanner.Text(), true
+	}
 }
 
 // sendRequest sends a request to the given URL.
diff --git a/gemini.go b/gemini.go
index f3e0c81..635622c 100644
--- a/gemini.go
+++ b/gemini.go
@@ -49,16 +49,16 @@ func init() {
 		defaultClientOnce.Do(func() { knownHosts.LoadDefault() })
 		return knownHosts.Lookup(hostname, cert)
 	}
-	DefaultClient.GetCertificate = func(hostname string, store *CertificateStore) *tls.Certificate {
-		if cert, err := store.Lookup(hostname); err == nil {
+	DefaultClient.GetCertificate = func(req *Request, store *ClientCertificateStore) *tls.Certificate {
+		if cert, err := store.Lookup(req.URL.Hostname(), req.URL.Path); err == nil {
 			return cert
 		}
 		duration := time.Hour
-		cert, err := NewCertificate(hostname, duration)
+		cert, err := NewCertificate("", duration)
 		if err != nil {
 			return nil
 		}
-		store.Add(hostname, cert)
+		store.Add(req.URL.Hostname()+req.URL.Path, cert)
 		return &cert
 	}
 }