diff --git a/api/v2/api_test.go b/api/v2/api_test.go
index 5cabf2e0..438e6f44 100644
--- a/api/v2/api_test.go
+++ b/api/v2/api_test.go
@@ -15,6 +15,7 @@ package v2
 
 import (
 	"bytes"
+	"encoding/json"
 	"fmt"
 	"io"
 	"net/http"
@@ -24,6 +25,7 @@ import (
 	"time"
 
 	"github.com/go-openapi/runtime"
+	"github.com/go-openapi/runtime/middleware"
 	"github.com/go-openapi/strfmt"
 	"github.com/prometheus/common/model"
 	"github.com/stretchr/testify/require"
@@ -269,32 +271,108 @@ func TestPostSilencesHandler(t *testing.T) {
 			},
 		} {
 			t.Run(tc.name, func(t *testing.T) {
-				silence, silenceBytes := createSilence(t, tc.sid, "silenceCreator", tc.start, tc.end)
-
 				api := API{
 					uptime:   time.Now(),
 					silences: silences,
 					logger:   log.NewNopLogger(),
 				}
 
-				r, err := http.NewRequest("POST", "/api/v2/silence/${tc.sid}", bytes.NewReader(silenceBytes))
-				require.NoError(t, err)
-
+				sil := createSilence(t, tc.sid, "silenceCreator", tc.start, tc.end)
 				w := httptest.NewRecorder()
-				p := runtime.TextProducer()
-				responder := api.postSilencesHandler(silence_ops.PostSilencesParams{
-					HTTPRequest: r,
-					Silence:     &silence,
-				})
-				responder.WriteResponse(w, p)
+				postSilences(t, w, api.postSilencesHandler, sil)
 				body, _ := io.ReadAll(w.Result().Body)
-
 				require.Equal(t, tc.expectedCode, w.Code, fmt.Sprintf("test case: %d, response: %s", i, string(body)))
 			})
 		}
 	})
 }
 
+func TestPostSilencesHandlerMissingIdCreatesSilence(t *testing.T) {
+	now := time.Now()
+	silences := newSilences(t)
+	api := API{
+		uptime:   time.Now(),
+		silences: silences,
+		logger:   log.NewNopLogger(),
+	}
+
+	// Create a new silence. It should be assigned a random UUID.
+	sil := createSilence(t, "", "silenceCreator", now.Add(time.Hour), now.Add(time.Hour*2))
+	w := httptest.NewRecorder()
+	postSilences(t, w, api.postSilencesHandler, sil)
+	require.Equal(t, http.StatusOK, w.Code)
+
+	// Get the silences from the API.
+	w = httptest.NewRecorder()
+	getSilences(t, w, api.getSilencesHandler)
+	require.Equal(t, http.StatusOK, w.Code)
+	var resp []open_api_models.GettableSilence
+	require.NoError(t, json.NewDecoder(w.Body).Decode(&resp))
+	require.Len(t, resp, 1)
+
+	// Change the ID. It should return 404 Not Found.
+	sil = open_api_models.PostableSilence{
+		ID:      "unknownID",
+		Silence: resp[0].Silence,
+	}
+	w = httptest.NewRecorder()
+	postSilences(t, w, api.postSilencesHandler, sil)
+	require.Equal(t, http.StatusNotFound, w.Code)
+
+	// Remove the ID. It should duplicate the silence with a different UUID.
+	sil = open_api_models.PostableSilence{
+		ID:      "",
+		Silence: resp[0].Silence,
+	}
+	w = httptest.NewRecorder()
+	postSilences(t, w, api.postSilencesHandler, sil)
+	require.Equal(t, http.StatusOK, w.Code)
+
+	// Get the silences from the API. There should now be 2 silences.
+	w = httptest.NewRecorder()
+	getSilences(t, w, api.getSilencesHandler)
+	require.Equal(t, http.StatusOK, w.Code)
+	require.NoError(t, json.NewDecoder(w.Body).Decode(&resp))
+	require.Len(t, resp, 2)
+	require.NotEqual(t, resp[0].ID, resp[1].ID)
+}
+
+func getSilences(
+	t *testing.T,
+	w *httptest.ResponseRecorder,
+	handlerFunc func(params silence_ops.GetSilencesParams) middleware.Responder,
+) {
+	r, err := http.NewRequest("GET", "/api/v2/silences", nil)
+	require.NoError(t, err)
+
+	p := runtime.TextProducer()
+	responder := handlerFunc(silence_ops.GetSilencesParams{
+		HTTPRequest: r,
+		Filter:      nil,
+	})
+	responder.WriteResponse(w, p)
+}
+
+func postSilences(
+	t *testing.T,
+	w *httptest.ResponseRecorder,
+	handlerFunc func(params silence_ops.PostSilencesParams) middleware.Responder,
+	sil open_api_models.PostableSilence,
+) {
+	b, err := json.Marshal(sil)
+	require.NoError(t, err)
+
+	r, err := http.NewRequest("POST", "/api/v2/silences", bytes.NewReader(b))
+	require.NoError(t, err)
+
+	p := runtime.TextProducer()
+	responder := handlerFunc(silence_ops.PostSilencesParams{
+		HTTPRequest: r,
+		Silence:     &sil,
+	})
+	responder.WriteResponse(w, p)
+}
+
 func TestCheckSilenceMatchesFilterLabels(t *testing.T) {
 	type test struct {
 		silenceMatchers []*silencepb.Matcher
diff --git a/api/v2/testing.go b/api/v2/testing.go
index c813d350..7665a19f 100644
--- a/api/v2/testing.go
+++ b/api/v2/testing.go
@@ -14,19 +14,17 @@
 package v2
 
 import (
-	"encoding/json"
 	"testing"
 	"time"
 
 	"github.com/go-openapi/strfmt"
-	"github.com/stretchr/testify/require"
 
 	open_api_models "github.com/prometheus/alertmanager/api/v2/models"
 	"github.com/prometheus/alertmanager/pkg/labels"
 	"github.com/prometheus/alertmanager/silence/silencepb"
 )
 
-func createSilence(t *testing.T, ID, creator string, start, ends time.Time) (open_api_models.PostableSilence, []byte) {
+func createSilence(t *testing.T, ID, creator string, start, ends time.Time) open_api_models.PostableSilence {
 	t.Helper()
 
 	comment := "test"
@@ -46,10 +44,7 @@ func createSilence(t *testing.T, ID, creator string, start, ends time.Time) (ope
 			Comment:   &comment,
 		},
 	}
-	b, err := json.Marshal(&sil)
-	require.NoError(t, err)
-
-	return sil, b
+	return sil
 }
 
 func createSilenceMatcher(t *testing.T, name, pattern string, matcherType silencepb.Matcher_Type) *silencepb.Matcher {