diff --git a/api/api.go b/api/api.go
index e372c8ea..5e468c56 100644
--- a/api/api.go
+++ b/api/api.go
@@ -15,6 +15,7 @@ package api
 
 import (
 	"encoding/json"
+	"errors"
 	"fmt"
 	"net/http"
 	"regexp"
@@ -540,6 +541,27 @@ func (api *API) setSilence(w http.ResponseWriter, r *http.Request) {
 		}, nil)
 		return
 	}
+
+	// This is an API only validation, it cannot be done internally
+	// because the expired silence is semantically important.
+	// But one should not be able to create expired silences, that
+	// won't have any use.
+	if sil.Expired() {
+		api.respondError(w, apiError{
+			typ: errorBadData,
+			err: errors.New("start time must not be equal to end time"),
+		}, nil)
+		return
+	}
+
+	if sil.EndsAt.Before(time.Now()) {
+		api.respondError(w, apiError{
+			typ: errorBadData,
+			err: errors.New("end time can't be in the past"),
+		}, nil)
+		return
+	}
+
 	psil, err := silenceToProto(&sil)
 	if err != nil {
 		api.respondError(w, apiError{
diff --git a/types/types.go b/types/types.go
index ce964102..29202ecf 100644
--- a/types/types.go
+++ b/types/types.go
@@ -356,6 +356,12 @@ type Silence struct {
 	Status SilenceStatus `json:"status"`
 }
 
+// Expired return if the silence is expired
+// meaning that both StartsAt and EndsAt are equal
+func (s *Silence) Expired() bool {
+	return s.StartsAt.Equal(s.EndsAt)
+}
+
 type SilenceStatus struct {
 	State SilenceState `json:"state"`
 }
diff --git a/types/types_test.go b/types/types_test.go
index ae143743..9953b8c0 100644
--- a/types/types_test.go
+++ b/types/types_test.go
@@ -82,3 +82,15 @@ func TestCalcSilenceState(t *testing.T) {
 	expected = CalcSilenceState(pastStartTime, pastEndTime)
 	require.Equal(t, SilenceStateExpired, expected)
 }
+
+func TestSilenceExpired(t *testing.T) {
+	now := time.Now()
+	silence := Silence{StartsAt: now, EndsAt: now}
+	require.True(t, silence.Expired())
+
+	silence = Silence{StartsAt: now.Add(time.Hour), EndsAt: now.Add(time.Hour)}
+	require.True(t, silence.Expired())
+
+	silence = Silence{StartsAt: now, EndsAt: now.Add(time.Hour)}
+	require.False(t, silence.Expired())
+}