diff --git a/packages/validator/src/services/proposerPreferences.ts b/packages/validator/src/services/proposerPreferences.ts
index 0c400a3bcb5c..29e161754156 100644
--- a/packages/validator/src/services/proposerPreferences.ts
+++ b/packages/validator/src/services/proposerPreferences.ts
@@ -29,7 +29,10 @@ type SubmittedAtEpoch = {dependentRoot: RootHex; slots: Set<Slot>};
  * dependent root for an epoch shifts (e.g. after a reorg) — detected by comparing the cached
  * `dependentRoot` reported by `BlockDutiesService` against the one we last submitted under.
  *
- * No-op pre-gloas.
+ * Proposers should broadcast their preferences before the fork so the proposer preference caches
+ * of beacon nodes and builders are warm for the first Gloas slots. We start submitting
+ * as soon as a duty's proposal slot is in Gloas, which is up to `SUBMIT_BEFORE_PROPOSAL_SLOTS`
+ * before the fork, so only the first few Gloas slots are affected by this pre-fork submission.
  */
 export class ProposerPreferencesService {
   private readonly submitted = new Map<Epoch, SubmittedAtEpoch>();
@@ -47,7 +50,10 @@ export class ProposerPreferencesService {
   }
 
   private runProposerPreferencesTask = async (slot: Slot): Promise<void> => {
-    if (!isForkPostGloas(this.config.getForkName(slot))) {
+    // Start running once the submission window (`slot + SUBMIT_BEFORE_PROPOSAL_SLOTS`) reaches
+    // Gloas, i.e. already in the epoch before the fork. This allows builders to prepare and
+    // submit bids for the first Gloas slots.
+    if (!isForkPostGloas(this.config.getForkName(slot + SUBMIT_BEFORE_PROPOSAL_SLOTS))) {
       return;
     }
 
@@ -82,6 +88,7 @@ export class ProposerPreferencesService {
       for (const duty of dutiesAtEpoch.data) {
         if (duty.slot <= slot) continue;
         if (duty.slot > slot + SUBMIT_BEFORE_PROPOSAL_SLOTS) continue;
+        if (!isForkPostGloas(this.config.getForkName(duty.slot))) continue;
         if (submission.slots.has(duty.slot)) continue;
 
         try {