diff --git a/pgxn/neon/file_cache.c b/pgxn/neon/file_cache.c
index 8cfa09bc87..0e316abd1d 100644
--- a/pgxn/neon/file_cache.c
+++ b/pgxn/neon/file_cache.c
@@ -205,6 +205,8 @@ bool AmPrewarmWorker;
 
 #define LFC_ENABLED() (lfc_ctl->limit != 0)
 
+PGDLLEXPORT void lfc_prewarm_main(Datum main_arg);
+
 /*
  * Close LFC file if opened.
  * All backends should close their LFC files once LFC is disabled.
@@ -2135,40 +2137,25 @@ local_cache_pages(PG_FUNCTION_ARGS)
 		SRF_RETURN_DONE(funcctx);
 }
 
-PG_FUNCTION_INFO_V1(approximate_working_set_size_seconds);
 
-Datum
-approximate_working_set_size_seconds(PG_FUNCTION_ARGS)
+/*
+ * Internal implementation of the approximate_working_set_size_seconds()
+ * function.
+ */
+int32
+lfc_approximate_working_set_size_seconds(time_t duration, bool reset)
 {
-	if (lfc_size_limit != 0)
-	{
-		int32 dc;
-		time_t duration = PG_ARGISNULL(0) ? (time_t)-1 : PG_GETARG_INT32(0);
-		LWLockAcquire(lfc_lock, LW_SHARED);
-		dc = (int32) estimateSHLL(&lfc_ctl->wss_estimation, duration);
-		LWLockRelease(lfc_lock);
-		PG_RETURN_INT32(dc);
-	}
-	PG_RETURN_NULL();
-}
+	int32		dc;
 
-PG_FUNCTION_INFO_V1(approximate_working_set_size);
+	if (lfc_size_limit == 0)
+		return -1;
 
-Datum
-approximate_working_set_size(PG_FUNCTION_ARGS)
-{
-	if (lfc_size_limit != 0)
-	{
-		int32 dc;
-		bool reset = PG_GETARG_BOOL(0);
-		LWLockAcquire(lfc_lock, reset ? LW_EXCLUSIVE : LW_SHARED);
-		dc = (int32) estimateSHLL(&lfc_ctl->wss_estimation, (time_t)-1);
-		if (reset)
-			memset(lfc_ctl->wss_estimation.regs, 0, sizeof lfc_ctl->wss_estimation.regs);
-		LWLockRelease(lfc_lock);
-		PG_RETURN_INT32(dc);
-	}
-	PG_RETURN_NULL();
+	LWLockAcquire(lfc_lock, LW_SHARED);
+	dc = (int32) estimateSHLL(&lfc_ctl->wss_estimation, duration);
+	if (reset)
+		memset(lfc_ctl->wss_estimation.regs, 0, sizeof lfc_ctl->wss_estimation.regs);
+	LWLockRelease(lfc_lock);
+	return dc;
 }
 
 PG_FUNCTION_INFO_V1(get_local_cache_state);
diff --git a/pgxn/neon/file_cache.h b/pgxn/neon/file_cache.h
index d5ac55d5ba..14e5d4f753 100644
--- a/pgxn/neon/file_cache.h
+++ b/pgxn/neon/file_cache.h
@@ -47,7 +47,8 @@ extern bool lfc_prefetch(NRelFileInfo rinfo, ForkNumber forknum, BlockNumber blk
 extern FileCacheState* lfc_get_state(size_t max_entries);
 extern void lfc_prewarm(FileCacheState* fcs, uint32 n_workers);
 
-PGDLLEXPORT void lfc_prewarm_main(Datum main_arg);
+extern int32 lfc_approximate_working_set_size_seconds(time_t duration, bool reset);
+
 
 static inline bool
 lfc_read(NRelFileInfo rinfo, ForkNumber forkNum, BlockNumber blkno,
diff --git a/pgxn/neon/neon.c b/pgxn/neon/neon.c
index 9e0ca16fed..7b749f1080 100644
--- a/pgxn/neon/neon.c
+++ b/pgxn/neon/neon.c
@@ -561,6 +561,8 @@ _PG_init(void)
 PG_FUNCTION_INFO_V1(pg_cluster_size);
 PG_FUNCTION_INFO_V1(backpressure_lsns);
 PG_FUNCTION_INFO_V1(backpressure_throttling_time);
+PG_FUNCTION_INFO_V1(approximate_working_set_size_seconds);
+PG_FUNCTION_INFO_V1(approximate_working_set_size);
 
 Datum
 pg_cluster_size(PG_FUNCTION_ARGS)
@@ -607,6 +609,34 @@ backpressure_throttling_time(PG_FUNCTION_ARGS)
 	PG_RETURN_UINT64(BackpressureThrottlingTime());
 }
 
+Datum
+approximate_working_set_size_seconds(PG_FUNCTION_ARGS)
+{
+	time_t		duration;
+	int32		dc;
+
+	duration = PG_ARGISNULL(0) ? (time_t) -1 : PG_GETARG_INT32(0);
+
+	dc = lfc_approximate_working_set_size_seconds(duration, false);
+	if (dc < 0)
+		PG_RETURN_NULL();
+	else
+		PG_RETURN_INT32(dc);
+}
+
+Datum
+approximate_working_set_size(PG_FUNCTION_ARGS)
+{
+	bool		reset = PG_GETARG_BOOL(0);
+	int32		dc;
+
+	dc = lfc_approximate_working_set_size_seconds(-1, reset);
+	if (dc < 0)
+		PG_RETURN_NULL();
+	else
+		PG_RETURN_INT32(dc);
+}
+
 #if PG_MAJORVERSION_NUM >= 16
 static void
 neon_shmem_startup_hook(void)