diff --git a/unittest/libmariadb/connection.c b/unittest/libmariadb/connection.c
index 049ffb34..6fa61c17 100644
--- a/unittest/libmariadb/connection.c
+++ b/unittest/libmariadb/connection.c
@@ -1623,6 +1623,8 @@ static int test_conc366(MYSQL *mysql)
   check_mysql_rc(rc, mysql);
 
   my= mysql_init(NULL);
+  if (plugindir)
+    mysql_options(my, MYSQL_PLUGIN_DIR, plugindir);
   if (!mysql_real_connect(my, hostname, "ede", "foo", schema, port, socketname, 0))
   {
     diag("Error: %s", mysql_error(my));
@@ -1633,7 +1635,10 @@ static int test_conc366(MYSQL *mysql)
   sprintf(query, "DROP USER 'ede'@'%s'", this_host);
   rc= mysql_query(mysql, query);
   check_mysql_rc(rc, mysql);
-  
+
+  sprintf(query, "UNINSTALL SONAME 'auth_ed25519'");
+  rc= mysql_query(mysql, query);
+  check_mysql_rc(rc, mysql);
 
   return OK;
 }
diff --git a/unittest/libmariadb/my_test.h b/unittest/libmariadb/my_test.h
index 0aa673cf..c265fa06 100644
--- a/unittest/libmariadb/my_test.h
+++ b/unittest/libmariadb/my_test.h
@@ -139,6 +139,7 @@ static char *username = 0;
 static int force_tls= 0;
 static uchar is_mariadb= 0;
 static char *this_host= 0;
+static char *plugindir= 0;
 static unsigned char travis_test= 0;
 /*
 static struct my_option test_options[] =
@@ -513,6 +514,8 @@ void get_envvars() {
       socketname= envvar;
     diag("socketname: %s", socketname);
   }
+  if ((envvar= getenv("MYSQL_TEST_PLUGINDIR")))
+    plugindir= envvar;
 }
 
 MYSQL *my_test_connect(MYSQL *mysql,