diff --git a/HISTORY b/HISTORY
index 2c594d27..8931c5be 100644
--- a/HISTORY
+++ b/HISTORY
@@ -1,3 +1,6 @@
+4.2.1   2018-??-??
+        repmgr: add sanity check for correct extension version (Ian)
+
 4.2     2018-10-24
         repmgr: add parameter "shutdown_check_timeout" for use by "standby switchover";
           GitHub #504 (Ian)
diff --git a/dbutils.c b/dbutils.c
index ef21f06c..70f4a036 100644
--- a/dbutils.c
+++ b/dbutils.c
@@ -1834,7 +1834,7 @@ atobool(const char *value)
 /* =================== */
 
 ExtensionStatus
-get_repmgr_extension_status(PGconn *conn)
+get_repmgr_extension_status(PGconn *conn, t_extension_versions *extversions)
 {
 	PQExpBufferData query;
 	PGresult   *res = NULL;
@@ -1845,7 +1845,11 @@ get_repmgr_extension_status(PGconn *conn)
 	initPQExpBuffer(&query);
 
 	appendPQExpBufferStr(&query,
-						 "	  SELECT ae.name, e.extname "
+						 "	  SELECT ae.name, e.extname, "
+						 "           ae.default_version, "
+						 "           (ae.default_version::numeric * 10)::INT AS available, "
+						 "           ae.installed_version, "
+						 "           (ae.installed_version::numeric * 10)::INT AS installed "
 						 "     FROM pg_catalog.pg_available_extensions ae "
 						 "LEFT JOIN pg_catalog.pg_extension e "
 						 "       ON e.extname=ae.name "
@@ -1868,7 +1872,24 @@ get_repmgr_extension_status(PGconn *conn)
 	/* 2. Check if extension installed */
 	else if (PQgetisnull(res, 0, 1) == 0)
 	{
-		status = REPMGR_INSTALLED;
+		int available_version = atoi(PQgetvalue(res, 0, 3));
+		int installed_version = atoi(PQgetvalue(res, 0, 5));
+
+		/* caller wants to know which versions are installed/available */
+		if (extversions != NULL)
+		{
+			strncpy(extversions->default_version, PQgetvalue(res, 0, 2), 7);
+			strncpy(extversions->installed_version, PQgetvalue(res, 0, 4), 7);
+		}
+
+		if (available_version > installed_version)
+		{
+			status = REPMGR_OLD_VERSION_INSTALLED;
+		}
+		else
+		{
+			status = REPMGR_INSTALLED;
+		}
 	}
 	else
 	{
diff --git a/dbutils.h b/dbutils.h
index 1976512e..a5b50d7a 100644
--- a/dbutils.h
+++ b/dbutils.h
@@ -47,6 +47,7 @@ typedef enum
 typedef enum
 {
 	REPMGR_INSTALLED = 0,
+	REPMGR_OLD_VERSION_INSTALLED,
 	REPMGR_AVAILABLE,
 	REPMGR_UNAVAILABLE,
 	REPMGR_UNKNOWN
@@ -104,6 +105,20 @@ typedef enum
 } BackupState;
 
 
+/*
+ * Struct to store extension version information
+ */
+
+typedef struct s_extension_versions {
+	char		default_version[8];
+	char		installed_version[8];
+} t_extension_versions;
+
+#define T_EXTENSION_VERSIONS_INITIALIZER { \
+	"", \
+	"", \
+}
+
 /*
  * Struct to store node information
  */
@@ -419,7 +434,7 @@ bool		repmgrd_is_paused(PGconn *conn);
 bool		repmgrd_pause(PGconn *conn, bool pause);
 
 /* extension functions */
-ExtensionStatus get_repmgr_extension_status(PGconn *conn);
+ExtensionStatus get_repmgr_extension_status(PGconn *conn, t_extension_versions *extversions);
 
 /* node management functions */
 void		checkpoint(PGconn *conn);
diff --git a/repmgr-action-bdr.c b/repmgr-action-bdr.c
index be6cc4a8..ff0e76c0 100644
--- a/repmgr-action-bdr.c
+++ b/repmgr-action-bdr.c
@@ -126,7 +126,7 @@ do_bdr_register(void)
 	}
 
 	/* check whether repmgr extension exists, and there are no non-BDR nodes registered */
-	extension_status = get_repmgr_extension_status(conn);
+	extension_status = get_repmgr_extension_status(conn, NULL);
 
 	if (extension_status == REPMGR_UNKNOWN)
 	{
@@ -232,7 +232,7 @@ do_bdr_register(void)
 				}
 
 				/* check repmgr schema exists, skip if not */
-				other_node_extension_status = get_repmgr_extension_status(bdr_node_conn);
+				other_node_extension_status = get_repmgr_extension_status(bdr_node_conn, NULL);
 
 				if (other_node_extension_status != REPMGR_INSTALLED)
 				{
@@ -442,7 +442,7 @@ do_bdr_unregister(void)
 		exit(ERR_BAD_CONFIG);
 	}
 
-	extension_status = get_repmgr_extension_status(conn);
+	extension_status = get_repmgr_extension_status(conn, NULL);
 	if (extension_status != REPMGR_INSTALLED)
 	{
 		log_error(_("repmgr is not installed on database \"%s\""), dbname);
diff --git a/repmgr-action-standby.c b/repmgr-action-standby.c
index 68c5fee0..8add98bd 100644
--- a/repmgr-action-standby.c
+++ b/repmgr-action-standby.c
@@ -4425,7 +4425,7 @@ check_source_server()
 	 * to be used as a standalone clone tool)
 	 */
 
-	extension_status = get_repmgr_extension_status(primary_conn);
+	extension_status = get_repmgr_extension_status(primary_conn, NULL);
 
 	if (extension_status != REPMGR_INSTALLED)
 	{
diff --git a/repmgr-client.c b/repmgr-client.c
index 4e7278a8..ac1d5937 100644
--- a/repmgr-client.c
+++ b/repmgr-client.c
@@ -2080,8 +2080,9 @@ create_repmgr_extension(PGconn *conn)
 	bool		is_superuser = false;
 	PGconn	   *superuser_conn = NULL;
 	PGconn	   *schema_create_conn = NULL;
+	t_extension_versions extversions = T_EXTENSION_VERSIONS_INITIALIZER;
 
-	extension_status = get_repmgr_extension_status(conn);
+	extension_status = get_repmgr_extension_status(conn, &extversions);
 
 	switch (extension_status)
 	{
@@ -2093,8 +2094,15 @@ create_repmgr_extension(PGconn *conn)
 			log_error(_("\"repmgr\" extension is not available"));
 			return false;
 
+		case REPMGR_OLD_VERSION_INSTALLED:
+			log_error(_("an older version of the \"repmgr\" extension is installed"));
+			log_detail(_("version %s is installed but newer version %s is available"),
+					   extversions.installed_version,
+					   extversions.default_version);
+			log_hint(_("execute \"ALTER EXTENSION repmgr UPGRADE\""));
+			return false;
+
 		case REPMGR_INSTALLED:
-			/* TODO: check version */
 			log_info(_("\"repmgr\" extension is already installed"));
 			return true;
 
diff --git a/repmgrd.c b/repmgrd.c
index 4e4776e9..180507ab 100644
--- a/repmgrd.c
+++ b/repmgrd.c
@@ -88,6 +88,7 @@ main(int argc, char **argv)
 
 	RecordStatus record_status;
 	ExtensionStatus extension_status = REPMGR_UNKNOWN;
+	t_extension_versions extversions = T_EXTENSION_VERSIONS_INITIALIZER;
 
 	FILE	   *fd;
 
@@ -389,7 +390,7 @@ main(int argc, char **argv)
 	 */
 
 	/* Check "repmgr" the extension is installed */
-	extension_status = get_repmgr_extension_status(local_conn);
+	extension_status = get_repmgr_extension_status(local_conn, &extversions);
 
 	if (extension_status != REPMGR_INSTALLED)
 	{
@@ -402,19 +403,32 @@ main(int argc, char **argv)
 			exit(ERR_DB_QUERY);
 		}
 
-		log_error(_("repmgr extension not found on this node"));
+		if (extension_status == REPMGR_OLD_VERSION_INSTALLED)
+		{
+			log_error(_("an older version of the \"repmgr\" extension is installed"));
+			log_detail(_("version %s is installed but newer version %s is available"),
+					   extversions.installed_version,
+					   extversions.default_version);
+			log_hint(_("verify the repmgr installation is updated properly before continuing"));
 
-		if (extension_status == REPMGR_AVAILABLE)
-		{
-			log_detail(_("repmgr extension is available but not installed in database \"%s\""),
-					   PQdb(local_conn));
 		}
-		else if (extension_status == REPMGR_UNAVAILABLE)
+		else
 		{
-			log_detail(_("repmgr extension is not available on this node"));
+			log_error(_("repmgr extension not found on this node"));
+
+			if (extension_status == REPMGR_AVAILABLE)
+			{
+				log_detail(_("repmgr extension is available but not installed in database \"%s\""),
+						   PQdb(local_conn));
+			}
+			else if (extension_status == REPMGR_UNAVAILABLE)
+			{
+				log_detail(_("repmgr extension is not available on this node"));
+			}
+
+			log_hint(_("check that this node is part of a repmgr cluster"));
 		}
 
-		log_hint(_("check that this node is part of a repmgr cluster"));
 		close_connection(&local_conn);
 		exit(ERR_BAD_CONFIG);
 	}