diff --git a/include/internal/quic_ackm.h b/include/internal/quic_ackm.h
index 1fedc08769..7574c97a96 100644
--- a/include/internal/quic_ackm.h
+++ b/include/internal/quic_ackm.h
@@ -263,6 +263,9 @@ int ossl_ackm_mark_packet_pseudo_lost(OSSL_ACKM *ackm,
  */
 OSSL_TIME ossl_ackm_get_pto_duration(OSSL_ACKM *ackm);
 
+/* Returns the largest acked PN in the given PN space. */
+QUIC_PN ossl_ackm_get_largest_acked(OSSL_ACKM *ackm, int pkt_space);
+
 # endif
 
 #endif
diff --git a/ssl/quic/quic_ackm.c b/ssl/quic/quic_ackm.c
index 4caf146c61..777d71ce53 100644
--- a/ssl/quic/quic_ackm.c
+++ b/ssl/quic/quic_ackm.c
@@ -1677,3 +1677,8 @@ OSSL_TIME ossl_ackm_get_pto_duration(OSSL_ACKM *ackm)
 
     return duration;
 }
+
+QUIC_PN ossl_ackm_get_largest_acked(OSSL_ACKM *ackm, int pkt_space)
+{
+    return ackm->largest_acked_pkt[pkt_space];
+}