diff --git a/Makefile b/Makefile
index ab90e59..9869ec9 100644
--- a/Makefile
+++ b/Makefile
@@ -1,7 +1,7 @@
 # contrib/pg_wait_sampling/Makefile
 
 MODULE_big = pg_wait_sampling
-OBJS = pg_wait_sampling.o collector.o compat.o
+OBJS = pg_wait_sampling.o collector.o
 
 EXTENSION = pg_wait_sampling
 EXTVERSION = 1.1
diff --git a/collector.c b/collector.c
index 9bb8cfb..2bfe534 100644
--- a/collector.c
+++ b/collector.c
@@ -26,6 +26,7 @@
 #include "utils/resowner.h"
 #include "pgstat.h"
 
+#include "compat.h"
 #include "pg_wait_sampling.h"
 
 static volatile sig_atomic_t shutdown_requested = false;
diff --git a/compat.c b/compat.h
similarity index 76%
rename from compat.c
rename to compat.h
index f2a57ae..3f471ce 100644
--- a/compat.c
+++ b/compat.h
@@ -1,11 +1,32 @@
+/*
+ * compat.h
+ *		Definitions for function wrappers compatible between PG versions.
+ *
+ * Copyright (c) 2015-2022, Postgres Professional
+ *
+ * IDENTIFICATION
+ *	  contrib/pg_wait_sampling/compat.h
+ */
+#ifndef __COMPAT_H__
+#define __COMPAT_H__
+
 #include "postgres.h"
 
 #include "access/tupdesc.h"
 #include "miscadmin.h"
+#include "storage/shm_mq.h"
 
-#include "pg_wait_sampling.h"
+static inline TupleDesc
+CreateTemplateTupleDescCompat(int nattrs, bool hasoid)
+{
+#if PG_VERSION_NUM >= 120000
+	return CreateTemplateTupleDesc(nattrs);
+#else
+	return CreateTemplateTupleDesc(nattrs, hasoid);
+#endif
+}
 
-inline void
+static inline void
 shm_mq_detach_compat(shm_mq_handle *mqh, shm_mq *mq)
 {
 #if PG_VERSION_NUM >= 100000
@@ -15,7 +36,7 @@ shm_mq_detach_compat(shm_mq_handle *mqh, shm_mq *mq)
 #endif
 }
 
-inline shm_mq_result
+static inline shm_mq_result
 shm_mq_send_compat(shm_mq_handle *mqh, Size nbytes, const void *data,
 				   bool nowait, bool force_flush)
 {
@@ -26,17 +47,7 @@ shm_mq_send_compat(shm_mq_handle *mqh, Size nbytes, const void *data,
 #endif
 }
 
-inline TupleDesc
-CreateTemplateTupleDescCompat(int nattrs, bool hasoid)
-{
-#if PG_VERSION_NUM >= 120000
-	return CreateTemplateTupleDesc(nattrs);
-#else
-	return CreateTemplateTupleDesc(nattrs, hasoid);
-#endif
-}
-
-inline void
+static inline void
 InitPostgresCompat(const char *in_dbname, Oid dboid,
 				   const char *username, Oid useroid,
 				   bool load_session_libraries,
@@ -53,3 +64,5 @@ InitPostgresCompat(const char *in_dbname, Oid dboid,
 	InitPostgres(in_dbname, dboid, username, useroid, out_dbname);
 #endif
 }
+
+#endif
diff --git a/pg_wait_sampling.c b/pg_wait_sampling.c
index 8c45f10..deda26c 100644
--- a/pg_wait_sampling.c
+++ b/pg_wait_sampling.c
@@ -34,6 +34,7 @@
 #include "utils/memutils.h" /* TopMemoryContext.  Actually for PG 9.6 only,
 							 * but there should be no harm for others. */
 
+#include "compat.h"
 #include "pg_wait_sampling.h"
 
 PG_MODULE_MAGIC;
diff --git a/pg_wait_sampling.h b/pg_wait_sampling.h
index 0de8d7b..a33d707 100644
--- a/pg_wait_sampling.h
+++ b/pg_wait_sampling.h
@@ -83,15 +83,4 @@ extern void register_wait_collector(void);
 extern void alloc_history(History *, int);
 extern PGDLLEXPORT void collector_main(Datum main_arg);
 
-extern void shm_mq_detach_compat(shm_mq_handle *mqh, shm_mq *mq);
-extern shm_mq_result shm_mq_send_compat(shm_mq_handle *mqh, Size nbytes,
-										const void *data, bool nowait,
-										bool force_flush);
-extern TupleDesc CreateTemplateTupleDescCompat(int nattrs, bool hasoid);
-extern void InitPostgresCompat(const char *in_dbname, Oid dboid,
-							   const char *username, Oid useroid,
-							   bool load_session_libraries,
-							   bool override_allow_connections,
-							   char *out_dbname);
-
 #endif