diff --git a/go.mod b/go.mod
index daab4218c91..576f6c0614f 100644
--- a/go.mod
+++ b/go.mod
@@ -197,7 +197,6 @@ require (
 	go.uber.org/goleak v1.3.0 // @grafana/grafana-search-and-storage
 	go.uber.org/mock v0.6.0 // @grafana/grafana-operator-experience-squad
 	go.uber.org/zap v1.27.0 // @grafana/identity-access-team
-	go.yaml.in/yaml/v2 v2.4.3 // @grafana/alerting-backend
 	go.yaml.in/yaml/v3 v3.0.4 // @grafana/alerting-backend
 	gocloud.dev v0.43.0 // @grafana/grafana-app-platform-squad
 	gocloud.dev/secrets/hashivault v0.43.0 // @grafana/grafana-operator-experience-squad
@@ -628,6 +627,7 @@ require (
 	go.opentelemetry.io/otel/sdk/metric v1.38.0 // indirect
 	go.opentelemetry.io/proto/otlp v1.7.1 // indirect
 	go.uber.org/multierr v1.11.0 // indirect
+	go.yaml.in/yaml/v2 v2.4.3 // indirect
 	go4.org/netipx v0.0.0-20230125063823-8449b0a6169f // indirect
 	golang.org/x/sys v0.38.0 // indirect
 	golang.org/x/telemetry v0.0.0-20251111182119-bc8e575c7b54 // indirect
diff --git a/pkg/services/ngalert/sender/notifier_test.go b/pkg/services/ngalert/sender/notifier_test.go
index e7e9aedec96..a8b452437c1 100644
--- a/pkg/services/ngalert/sender/notifier_test.go
+++ b/pkg/services/ngalert/sender/notifier_test.go
@@ -28,6 +28,7 @@ import (
 	"net/http/httptest"
 	"net/url"
 	"strconv"
+	"strings"
 	"testing"
 	"time"
 
@@ -38,7 +39,7 @@ import (
 	"github.com/prometheus/common/promslog"
 	"github.com/stretchr/testify/require"
 	"go.uber.org/atomic"
-	"go.yaml.in/yaml/v2"
+	"go.yaml.in/yaml/v3"
 
 	"github.com/prometheus/prometheus/config"
 	"github.com/prometheus/prometheus/discovery"
@@ -660,11 +661,10 @@ alerting:
   alertmanagers:
   - static_configs:
 `
-	err := yaml.UnmarshalStrict([]byte(s), cfg)
-	require.NoError(t, err, "Unable to load YAML config.")
+	mustStrictlyDecodeConfig(t, strings.NewReader(s), cfg)
 	require.Len(t, cfg.AlertingConfig.AlertmanagerConfigs, 1)
 
-	err = n.ApplyConfig(cfg, nil)
+	err := n.ApplyConfig(cfg, nil)
 	require.NoError(t, err, "Error applying the config.")
 
 	tgs := make(map[string][]*targetgroup.Group)
@@ -711,11 +711,10 @@ alerting:
         regex: 'alertmanager:9093'
         action: drop
 `
-	err := yaml.UnmarshalStrict([]byte(s), cfg)
-	require.NoError(t, err, "Unable to load YAML config.")
+	mustStrictlyDecodeConfig(t, strings.NewReader(s), cfg)
 	require.Len(t, cfg.AlertingConfig.AlertmanagerConfigs, 1)
 
-	err = n.ApplyConfig(cfg, nil)
+	err := n.ApplyConfig(cfg, nil)
 	require.NoError(t, err, "Error applying the config.")
 
 	tgs := make(map[string][]*targetgroup.Group)
@@ -1091,7 +1090,7 @@ alerting:
       - foo.json
 `
 	// 1. Ensure known alertmanagers are not dropped during ApplyConfig.
-	require.NoError(t, yaml.UnmarshalStrict([]byte(s), cfg))
+	mustStrictlyDecodeConfig(t, strings.NewReader(s), cfg)
 	require.Len(t, cfg.AlertingConfig.AlertmanagerConfigs, 1)
 
 	// First, apply the config and reload.
@@ -1117,7 +1116,7 @@ alerting:
     - files:
       - foo.json
 `
-	require.NoError(t, yaml.UnmarshalStrict([]byte(s), cfg))
+	mustStrictlyDecodeConfig(t, strings.NewReader(s), cfg)
 	require.Len(t, cfg.AlertingConfig.AlertmanagerConfigs, 2)
 
 	require.NoError(t, n.ApplyConfig(cfg, nil))
@@ -1140,7 +1139,7 @@ alerting:
     - files:
       - foo.json
 `
-	require.NoError(t, yaml.UnmarshalStrict([]byte(s), cfg))
+	mustStrictlyDecodeConfig(t, strings.NewReader(s), cfg)
 	require.Len(t, cfg.AlertingConfig.AlertmanagerConfigs, 2)
 
 	require.NoError(t, n.ApplyConfig(cfg, nil))
@@ -1167,9 +1166,22 @@ alerting:
       regex: 'doesntmatter:1234'
       action: drop
 `
-	require.NoError(t, yaml.UnmarshalStrict([]byte(s), cfg))
+	mustStrictlyDecodeConfig(t, strings.NewReader(s), cfg)
 	require.Len(t, cfg.AlertingConfig.AlertmanagerConfigs, 2)
 
 	require.NoError(t, n.ApplyConfig(cfg, nil))
 	require.Empty(t, n.Alertmanagers())
 }
+
+// Maintain strict yaml decode behavior from v2: https://github.com/go-yaml/yaml/issues/639#issuecomment-666935833
+func mustStrictlyDecodeConfig(t testing.TB, r io.Reader, cfg *config.Config) {
+	t.Helper()
+
+	dec := yaml.NewDecoder(r)
+	dec.KnownFields(true)
+
+	err := dec.Decode(cfg)
+	if err != nil {
+		require.Equal(t, io.EOF, err, "Unable to load YAML config.")
+	}
+}