diff --git a/include/mosquitto_plugin.h b/include/mosquitto_plugin.h
index 18315375..31af29ad 100644
--- a/include/mosquitto_plugin.h
+++ b/include/mosquitto_plugin.h
@@ -21,9 +21,12 @@ Contributors:
 extern "C" {
 #endif
 
-#define MOSQ_AUTH_PLUGIN_VERSION 5
+/* The generic plugin interface starts at version 5 */
 #define MOSQ_PLUGIN_VERSION 5
 
+/* The old auth only interface stopped at version 4 */
+#define MOSQ_AUTH_PLUGIN_VERSION 4
+
 #define MOSQ_ACL_NONE 0x00
 #define MOSQ_ACL_READ 0x01
 #define MOSQ_ACL_WRITE 0x02
@@ -113,13 +116,15 @@ struct mosquitto_acl_msg {
  * ========================================================================= */
 
 /*
- * Function: mosquitto_auth_plugin_version
+ * Function: mosquitto_plugin_version
  *
- * The broker will call this function immediately after loading the plugin to
- * check it is a supported plugin version. Your code must simply return
- * the plugin interface version you support, i.e. 5.
+ * The broker will attempt to call this function immediately after loading the
+ * plugin to check it is a supported plugin version. Your code must simply
+ * return the plugin interface version you support, i.e. 5.
+ *
+ * The supported_versions array tells you which plugin versions the broker supports.
  */
-int mosquitto_plugin_version(void);
+int mosquitto_plugin_version(int supported_version_count, const int *supported_versions);
 
 /*
  * Function: mosquitto_auth_plugin_init
diff --git a/src/security.c b/src/security.c
index ebf21652..0cc09077 100644
--- a/src/security.c
+++ b/src/security.c
@@ -27,6 +27,7 @@ Contributors:
 #include "utlist.h"
 
 typedef int (*FUNC_auth_plugin_version)(void);
+typedef int (*FUNC_plugin_version)(int, const int *);
 
 static int security__cleanup_single(struct mosquitto__security_options *opts, bool reload);
 
@@ -287,10 +288,13 @@ int security__load_v4(struct mosquitto__auth_plugin *plugin, struct mosquitto_op
 static int security__module_init_single(struct mosquitto__listener *listener, struct mosquitto__security_options *opts)
 {
 	void *lib;
-	int (*plugin_version)(void) = NULL;
+	int (*plugin_version)(int, const int*) = NULL;
+	int (*plugin_auth_version)(void) = NULL;
 	int version;
 	int i;
 	int rc;
+	const int plugin_versions[] = {5, 4, 3, 2};
+	int plugin_version_count = sizeof(plugin_versions)/sizeof(int);
 
 	if(opts->auth_plugin_config_count == 0){
 		return MOSQ_ERR_SUCCESS;
@@ -311,16 +315,17 @@ static int security__module_init_single(struct mosquitto__listener *listener, st
 			}
 
 			opts->auth_plugin_configs[i].plugin.lib = NULL;
-			if(!(plugin_version = (FUNC_auth_plugin_version)LIB_SYM(lib, "mosquitto_plugin_version"))){
-				if(!(plugin_version = (FUNC_auth_plugin_version)LIB_SYM(lib, "mosquitto_auth_plugin_version"))){
-					log__printf(NULL, MOSQ_LOG_ERR,
-							"Error: Unable to load auth plugin function mosquitto_auth_plugin_version() or mosquitto_plugin_version().");
-					LIB_ERROR();
-					LIB_CLOSE(lib);
-					return 1;
-				}
+			if((plugin_version = (FUNC_plugin_version)LIB_SYM(lib, "mosquitto_plugin_version"))){
+				version = plugin_version(plugin_version_count, plugin_versions);
+			}else if((plugin_auth_version = (FUNC_auth_plugin_version)LIB_SYM(lib, "mosquitto_auth_plugin_version"))){
+				version = plugin_auth_version();
+			}else{
+				log__printf(NULL, MOSQ_LOG_ERR,
+						"Error: Unable to load auth plugin function mosquitto_auth_plugin_version() or mosquitto_plugin_version().");
+				LIB_ERROR();
+				LIB_CLOSE(lib);
+				return 1;
 			}
-			version = plugin_version();
 			opts->auth_plugin_configs[i].plugin.version = version;
 			if(version == 5){
 				rc = plugin__load_v5(