diff --git a/services/api/service.go b/services/api/service.go
index ff980db1..fb787962 100644
--- a/services/api/service.go
+++ b/services/api/service.go
@@ -1563,6 +1563,38 @@ func (api *RelayAPI) checkSubmissionSlotDetails(w http.ResponseWriter, log *logr
 	return true
 }
 
+func (api *RelayAPI) checkBuilderEntry(w http.ResponseWriter, log *logrus.Entry, builderPubkey phase0.BLSPubKey) (*blockBuilderCacheEntry, bool) {
+	builderEntry, ok := api.blockBuildersCache[builderPubkey.String()]
+	if !ok {
+		log.Warnf("unable to read builder: %s from the builder cache, using low-prio and no collateral", builderPubkey.String())
+		builderEntry = &blockBuilderCacheEntry{
+			status: common.BuilderStatus{
+				IsHighPrio:    false,
+				IsOptimistic:  false,
+				IsBlacklisted: false,
+			},
+			collateral: big.NewInt(0),
+		}
+	}
+
+	if builderEntry.status.IsBlacklisted {
+		log.Info("builder is blacklisted")
+		time.Sleep(200 * time.Millisecond)
+		w.WriteHeader(http.StatusOK)
+		return builderEntry, false
+	}
+
+	// In case only high-prio requests are accepted, fail others
+	if api.ffDisableLowPrioBuilders && !builderEntry.status.IsHighPrio {
+		log.Info("rejecting low-prio builder (ff-disable-low-prio-builders)")
+		time.Sleep(200 * time.Millisecond)
+		w.WriteHeader(http.StatusOK)
+		return builderEntry, false
+	}
+
+	return builderEntry, true
+}
+
 func (api *RelayAPI) handleSubmitNewBlock(w http.ResponseWriter, req *http.Request) {
 	var pf common.Profile
 	var prevTime, nextTime time.Time
@@ -1677,36 +1709,15 @@ func (api *RelayAPI) handleSubmitNewBlock(w http.ResponseWriter, req *http.Reque
 	}
 
 	builderPubkey := payload.BuilderPubkey()
-	builderEntry, ok := api.blockBuildersCache[builderPubkey.String()]
+	builderEntry, ok := api.checkBuilderEntry(w, log, builderPubkey)
 	if !ok {
-		log.Warnf("unable to read builder: %s from the builder cache, using low-prio and no collateral", builderPubkey.String())
-		builderEntry = &blockBuilderCacheEntry{
-			status: common.BuilderStatus{
-				IsHighPrio:    false,
-				IsOptimistic:  false,
-				IsBlacklisted: false,
-			},
-			collateral: big.NewInt(0),
-		}
-	}
-	log = log.WithField("builderIsHighPrio", builderEntry.status.IsHighPrio)
-
-	if builderEntry.status.IsBlacklisted {
-		log.Info("builder is blacklisted")
-		time.Sleep(200 * time.Millisecond)
-		w.WriteHeader(http.StatusOK)
 		return
 	}
 
-	// In case only high-prio requests are accepted, fail others
-	if api.ffDisableLowPrioBuilders && !builderEntry.status.IsHighPrio {
-		log.Info("rejecting low-prio builder (ff-disable-low-prio-builders)")
-		time.Sleep(200 * time.Millisecond)
-		w.WriteHeader(http.StatusOK)
-		return
-	}
-
-	log = log.WithField("timestampAfterChecks1", time.Now().UTC().UnixMilli())
+	log = log.WithFields(logrus.Fields{
+		"builderIsHighPrio":     builderEntry.status.IsHighPrio,
+		"timestampAfterChecks1": time.Now().UTC().UnixMilli(),
+	})
 
 	gasLimit, ok := api.checkSubmissionFeeRecipient(w, log, payload)
 	if !ok {
diff --git a/services/api/service_test.go b/services/api/service_test.go
index 2b5ebb52..b17b6afd 100644
--- a/services/api/service_test.go
+++ b/services/api/service_test.go
@@ -36,6 +36,7 @@ const (
 	testParentHash      = "0xbd3291854dc822b7ec585925cda0e18f06af28fa2886e15f52d52dd4b6f94ed6"
 	testWithdrawalsRoot = "0x7f6d156912a4cb1e74ee37e492ad883f7f7ac856d987b3228b517e490aa0189e"
 	testPrevRandao      = "0x9962816e9d0a39fd4c80935338a741dc916d1545694e41eb5a505e1a3098f9e4"
+	testBuilderPubkey   = "0xfa1ed37c3553d0ce1e9349b2c5063cf6e394d231c8d3e0df75e9462257c081543086109ffddaacc0aa76f33dc9661c83"
 )
 
 var (
@@ -577,9 +578,9 @@ func TestCheckSubmissionFeeRecipient(t *testing.T) {
 			w := httptest.NewRecorder()
 			logger := logrus.New()
 			log := logrus.NewEntry(logger)
-			gasLimit, cont := backend.relay.checkSubmissionFeeRecipient(w, log, tc.payload)
+			gasLimit, ok := backend.relay.checkSubmissionFeeRecipient(w, log, tc.payload)
 			require.Equal(t, tc.expectGasLimit, gasLimit)
-			require.Equal(t, tc.expectOk, cont)
+			require.Equal(t, tc.expectOk, ok)
 		})
 	}
 }
@@ -723,8 +724,8 @@ func TestCheckSubmissionPayloadAttrs(t *testing.T) {
 			w := httptest.NewRecorder()
 			logger := logrus.New()
 			log := logrus.NewEntry(logger)
-			cont := backend.relay.checkSubmissionPayloadAttrs(w, log, tc.payload)
-			require.Equal(t, tc.expectOk, cont)
+			ok := backend.relay.checkSubmissionPayloadAttrs(w, log, tc.payload)
+			require.Equal(t, tc.expectOk, ok)
 		})
 	}
 }
@@ -790,8 +791,71 @@ func TestCheckSubmissionSlotDetails(t *testing.T) {
 			w := httptest.NewRecorder()
 			logger := logrus.New()
 			log := logrus.NewEntry(logger)
-			cont := backend.relay.checkSubmissionSlotDetails(w, log, headSlot, tc.payload)
-			require.Equal(t, tc.expectOk, cont)
+			ok := backend.relay.checkSubmissionSlotDetails(w, log, headSlot, tc.payload)
+			require.Equal(t, tc.expectOk, ok)
+		})
+	}
+}
+
+func TestCheckBuilderEntry(t *testing.T) {
+	builderPubkeyByte, err := hexutil.Decode(testBuilderPubkey)
+	require.NoError(t, err)
+	builderPubkey := phase0.BLSPubKey(builderPubkeyByte)
+	diffPubkey := builderPubkey
+	diffPubkey[0] = 0xff
+	cases := []struct {
+		description string
+		entry       *blockBuilderCacheEntry
+		pk          phase0.BLSPubKey
+		expectOk    bool
+	}{
+		{
+			description: "success",
+			entry: &blockBuilderCacheEntry{
+				status: common.BuilderStatus{
+					IsHighPrio: true,
+				},
+			},
+			pk:       builderPubkey,
+			expectOk: true,
+		},
+		{
+			description: "failure_blacklisted",
+			entry: &blockBuilderCacheEntry{
+				status: common.BuilderStatus{
+					IsBlacklisted: true, // set blacklisted to true to cause failure
+				},
+			},
+			pk:       builderPubkey,
+			expectOk: false,
+		},
+		{
+			description: "failure_low_prio",
+			entry: &blockBuilderCacheEntry{
+				status: common.BuilderStatus{
+					IsHighPrio: false, // set low-prio to cause failure
+				},
+			},
+			pk:       builderPubkey,
+			expectOk: false,
+		},
+		{
+			description: "failure_nil_entry_low_prio",
+			entry:       nil,
+			pk:          diffPubkey, // set to different pubkey, so no entry is found
+			expectOk:    false,
+		},
+	}
+	for _, tc := range cases {
+		t.Run(tc.description, func(t *testing.T) {
+			_, _, backend := startTestBackend(t)
+			backend.relay.blockBuildersCache[tc.pk.String()] = tc.entry
+			backend.relay.ffDisableLowPrioBuilders = true
+			w := httptest.NewRecorder()
+			logger := logrus.New()
+			log := logrus.NewEntry(logger)
+			_, ok := backend.relay.checkBuilderEntry(w, log, builderPubkey)
+			require.Equal(t, tc.expectOk, ok)
 		})
 	}
 }