diff --git a/component/prometheus/relabel/relabel.go b/component/prometheus/relabel/relabel.go
index 349c5eeb1006..0f3b0c6dc9ac 100644
--- a/component/prometheus/relabel/relabel.go
+++ b/component/prometheus/relabel/relabel.go
@@ -56,6 +56,14 @@ func (arg *Arguments) SetToDefault() {
 	}
 }
 
+// Validate implements river.Validator.
+func (arg *Arguments) Validate() error {
+	if arg.CacheSize <= 0 {
+		return fmt.Errorf("max_cache_size must be greater than 0 and is %d", arg.CacheSize)
+	}
+	return nil
+}
+
 // Exports holds values which are exported by the prometheus.relabel component.
 type Exports struct {
 	Receiver storage.Appendable `river:"receiver,attr"`
diff --git a/component/prometheus/relabel/relabel_test.go b/component/prometheus/relabel/relabel_test.go
index c6d2b2699031..d029498555b8 100644
--- a/component/prometheus/relabel/relabel_test.go
+++ b/component/prometheus/relabel/relabel_test.go
@@ -44,11 +44,22 @@ func TestUpdateReset(t *testing.T) {
 	relabeller.relabel(0, lbls)
 	require.True(t, relabeller.cache.Len() == 1)
 	_ = relabeller.Update(Arguments{
+		CacheSize:            100000,
 		MetricRelabelConfigs: []*flow_relabel.Config{},
 	})
 	require.True(t, relabeller.cache.Len() == 0)
 }
 
+func TestValidator(t *testing.T) {
+	args := Arguments{CacheSize: 0}
+	err := args.Validate()
+	require.Error(t, err)
+
+	args.CacheSize = 1
+	err = args.Validate()
+	require.NoError(t, err)
+}
+
 func TestNil(t *testing.T) {
 	ls := labelstore.New(nil, prom.DefaultRegisterer)
 	fanout := prometheus.NewInterceptor(nil, ls, prometheus.WithAppendHook(func(ref storage.SeriesRef, _ labels.Labels, _ int64, _ float64, _ storage.Appender) (storage.SeriesRef, error) {
@@ -72,6 +83,7 @@ func TestNil(t *testing.T) {
 				Action:       "drop",
 			},
 		},
+		CacheSize: 100000,
 	})
 	require.NotNil(t, relabeller)
 	require.NoError(t, err)
@@ -129,7 +141,6 @@ func BenchmarkCache(b *testing.B) {
 
 	lbls := labels.FromStrings("__address__", "localhost")
 	app := entry.Appender(context.Background())
-
 	for i := 0; i < b.N; i++ {
 		app.Append(0, lbls, time.Now().UnixMilli(), 0)
 	}
@@ -161,6 +172,7 @@ func generateRelabel(t *testing.T) *Component {
 				Action:       "replace",
 			},
 		},
+		CacheSize: 100_000,
 	})
 	require.NotNil(t, relabeller)
 	require.NoError(t, err)