diff --git a/src/backend/storage/file/fd.c b/src/backend/storage/file/fd.c
index 3c2a2fbef7..16b3e8f905 100644
--- a/src/backend/storage/file/fd.c
+++ b/src/backend/storage/file/fd.c
@@ -3886,7 +3886,7 @@ data_sync_elevel(int elevel)
 }
 
 bool
-check_io_direct(char **newval, void **extra, GucSource source)
+check_debug_io_direct(char **newval, void **extra, GucSource source)
 {
 	bool		result = true;
 	int			flags;
@@ -3960,7 +3960,7 @@ check_io_direct(char **newval, void **extra, GucSource source)
 	if (!result)
 		return result;
 
-	/* Save the flags in *extra, for use by assign_io_direct */
+	/* Save the flags in *extra, for use by assign_debug_io_direct */
 	*extra = guc_malloc(ERROR, sizeof(int));
 	*((int *) *extra) = flags;
 
@@ -3968,7 +3968,7 @@ check_io_direct(char **newval, void **extra, GucSource source)
 }
 
 extern void
-assign_io_direct(const char *newval, void *extra)
+assign_debug_io_direct(const char *newval, void *extra)
 {
 	int		   *flags = (int *) extra;
 
diff --git a/src/backend/utils/misc/guc_tables.c b/src/backend/utils/misc/guc_tables.c
index 15b51f2c5b..45b93fe0f9 100644
--- a/src/backend/utils/misc/guc_tables.c
+++ b/src/backend/utils/misc/guc_tables.c
@@ -563,7 +563,7 @@ static char *datestyle_string;
 static char *server_encoding_string;
 static char *server_version_string;
 static int	server_version_num;
-static char *io_direct_string;
+static char *debug_io_direct_string;
 
 #ifdef HAVE_SYSLOG
 #define	DEFAULT_SYSLOG_FACILITY LOG_LOCAL0
@@ -4544,9 +4544,9 @@ struct config_string ConfigureNamesString[] =
 			NULL,
 			GUC_LIST_INPUT | GUC_NOT_IN_SAMPLE
 		},
-		&io_direct_string,
+		&debug_io_direct_string,
 		"",
-		check_io_direct, assign_io_direct, NULL
+		check_debug_io_direct, assign_debug_io_direct, NULL
 	},
 
 	/* End-of-list marker */
diff --git a/src/include/utils/guc_hooks.h b/src/include/utils/guc_hooks.h
index 2ecb9fc086..952293a1c3 100644
--- a/src/include/utils/guc_hooks.h
+++ b/src/include/utils/guc_hooks.h
@@ -49,6 +49,8 @@ extern bool check_cluster_name(char **newval, void **extra, GucSource source);
 extern const char *show_data_directory_mode(void);
 extern bool check_datestyle(char **newval, void **extra, GucSource source);
 extern void assign_datestyle(const char *newval, void *extra);
+extern bool check_debug_io_direct(char **newval, void **extra, GucSource source);
+extern void assign_debug_io_direct(const char *newval, void *extra);
 extern bool check_default_table_access_method(char **newval, void **extra,
 											  GucSource source);
 extern bool check_default_tablespace(char **newval, void **extra,
@@ -157,7 +159,5 @@ extern bool check_wal_consistency_checking(char **newval, void **extra,
 										   GucSource source);
 extern void assign_wal_consistency_checking(const char *newval, void *extra);
 extern void assign_xlog_sync_method(int new_sync_method, void *extra);
-extern bool check_io_direct(char **newval, void **extra, GucSource source);
-extern void assign_io_direct(const char *newval, void *extra);
 
 #endif							/* GUC_HOOKS_H */