diff --git a/khatru/expiration.go b/khatru/expiration.go
index 997e259..21af2a7 100644
--- a/khatru/expiration.go
+++ b/khatru/expiration.go
@@ -155,14 +155,14 @@ func (rl *Relay) StartExpirationManager(
 	}
 
 	go rl.expirationManager.start(rl.ctx)
-	rl.Info.AddSupportedNIP(40)
+	rl.Info.AddSupportedNIP("40")
 }
 
 func (rl *Relay) DisableExpirationManager() {
 	rl.expirationManager.stop()
 	rl.expirationManager = nil
 
-	idx := slices.Index(rl.Info.SupportedNIPs, 40)
+	idx := slices.Index(rl.Info.SupportedNIPs, "40")
 	if idx != -1 {
 		rl.Info.SupportedNIPs[idx] = rl.Info.SupportedNIPs[len(rl.Info.SupportedNIPs)-1]
 		rl.Info.SupportedNIPs = rl.Info.SupportedNIPs[0 : len(rl.Info.SupportedNIPs)-1]
diff --git a/khatru/grasp/server.go b/khatru/grasp/server.go
index 7ddc404..434d756 100644
--- a/khatru/grasp/server.go
+++ b/khatru/grasp/server.go
@@ -31,7 +31,7 @@ func New(rl *khatru.Relay, repositoryDir string) *GraspServer {
 		},
 	}
 
-	rl.Info.AddSupportedNIP(34)
+	rl.Info.AddSupportedNIP("34")
 	rl.Info.SupportedGrasps = append(rl.Info.SupportedGrasps, "GRASP-01")
 
 	base := rl.Router()
diff --git a/khatru/nip11.go b/khatru/nip11.go
index a72af76..f82b616 100644
--- a/khatru/nip11.go
+++ b/khatru/nip11.go
@@ -12,13 +12,13 @@ func (rl *Relay) HandleNIP11(w http.ResponseWriter, r *http.Request) {
 	info := *rl.Info
 
 	if nil != rl.DeleteEvent {
-		info.AddSupportedNIP(9)
+		info.AddSupportedNIP("9")
 	}
 	if nil != rl.Count {
-		info.AddSupportedNIP(45)
+		info.AddSupportedNIP("45")
 	}
 	if rl.Negentropy {
-		info.AddSupportedNIP(77)
+		info.AddSupportedNIP("77")
 	}
 
 	// resolve relative icon and banner URLs against base URL
diff --git a/khatru/relay.go b/khatru/relay.go
index 4355072..448bcb4 100644
--- a/khatru/relay.go
+++ b/khatru/relay.go
@@ -30,7 +30,7 @@ func NewRelay() *Relay {
 		Info: &nip11.RelayInformationDocument{
 			Software:      "https://pkg.go.dev/fiatjaf.com/nostr/khatru",
 			Version:       "n/a",
-			SupportedNIPs: []any{1, 11, 42, 70, 86},
+			SupportedNIPs: []string{"1", "11", "42", "70", "86"},
 		},
 
 		upgrader: websocket.Upgrader{
diff --git a/nip11/nip11_test.go b/nip11/nip11_test.go
index f94a9e2..e13d03d 100644
--- a/nip11/nip11_test.go
+++ b/nip11/nip11_test.go
@@ -9,30 +9,30 @@ import (
 
 func TestAddSupportedNIP(t *testing.T) {
 	info := RelayInformationDocument{}
-	info.AddSupportedNIP(12)
-	info.AddSupportedNIP(12)
-	info.AddSupportedNIP(13)
-	info.AddSupportedNIP(1)
-	info.AddSupportedNIP(12)
-	info.AddSupportedNIP(44)
-	info.AddSupportedNIP(2)
-	info.AddSupportedNIP(13)
-	info.AddSupportedNIP(2)
-	info.AddSupportedNIP(13)
-	info.AddSupportedNIP(0)
-	info.AddSupportedNIP(17)
-	info.AddSupportedNIP(19)
-	info.AddSupportedNIP(1)
-	info.AddSupportedNIP(18)
+	info.AddSupportedNIP("12")
+	info.AddSupportedNIP("12")
+	info.AddSupportedNIP("13")
+	info.AddSupportedNIP("1")
+	info.AddSupportedNIP("12")
+	info.AddSupportedNIP("44")
+	info.AddSupportedNIP("2")
+	info.AddSupportedNIP("13")
+	info.AddSupportedNIP("2")
+	info.AddSupportedNIP("13")
+	info.AddSupportedNIP("0")
+	info.AddSupportedNIP("17")
+	info.AddSupportedNIP("19")
+	info.AddSupportedNIP("1")
+	info.AddSupportedNIP("18")
 
-	assert.Contains(t, info.SupportedNIPs, 0, 1, 2, 12, 13, 17, 18, 19, 44)
+	assert.Contains(t, info.SupportedNIPs, "0", "1", "2", "12", "13", "17", "18", "19", "44")
 }
 
 func TestAddSupportedNIPs(t *testing.T) {
 	info := RelayInformationDocument{}
-	info.AddSupportedNIPs([]int{0, 1, 2, 12, 13, 17, 18, 19, 44})
+	info.AddSupportedNIPs([]int{"0", "1", "2", "12", "13", "17", "18", "19", "44"})
 
-	assert.Contains(t, info.SupportedNIPs, 0, 1, 2, 12, 13, 17, 18, 19, 44)
+	assert.Contains(t, info.SupportedNIPs, "0", "1", "2", "12", "13", "17", "18", "19", "44")
 }
 
 func TestFetch(t *testing.T) {
diff --git a/nip11/types.go b/nip11/types.go
index 7df9463..dce5be8 100644
--- a/nip11/types.go
+++ b/nip11/types.go
@@ -14,7 +14,7 @@ type RelayInformationDocument struct {
 	PubKey        *nostr.PubKey `json:"pubkey,omitempty"`
 	Self          *nostr.PubKey `json:"self,omitempty"`
 	Contact       string        `json:"contact,omitempty"`
-	SupportedNIPs []any         `json:"supported_nips,omitempty"`
+	SupportedNIPs []string      `json:"supported_nips,omitempty"`
 	Software      string        `json:"software,omitempty"`
 	Version       string        `json:"version,omitempty"`
 
@@ -33,16 +33,16 @@ type RelayInformationDocument struct {
 	SupportedGrasps []string `json:"supported_grasps,omitempty"`
 }
 
-func (info *RelayInformationDocument) AddSupportedNIP(number int) {
-	idx := slices.IndexFunc(info.SupportedNIPs, func(n any) bool { return n == number })
+func (info *RelayInformationDocument) AddSupportedNIP(nip string) {
+	idx := slices.IndexFunc(info.SupportedNIPs, func(n string) bool { return n == nip })
 	if idx != -1 {
 		return
 	}
 
-	info.SupportedNIPs = append(info.SupportedNIPs, number)
+	info.SupportedNIPs = append(info.SupportedNIPs, nip)
 }
 
-func (info *RelayInformationDocument) AddSupportedNIPs(numbers []int) {
+func (info *RelayInformationDocument) AddSupportedNIPs(numbers []string) {
 	for _, n := range numbers {
 		info.AddSupportedNIP(n)
 	}