diff --git a/plugins/auth/CMakeLists.txt b/plugins/auth/CMakeLists.txt
index 07688bed..3d2ede14 100644
--- a/plugins/auth/CMakeLists.txt
+++ b/plugins/auth/CMakeLists.txt
@@ -20,6 +20,13 @@ ELSE()
   UNSET(CRYPTO_PLUGIN)
 ENDIF()
 
+# GCC < 3.9 does not support thread-local storage in C
+IF(CMAKE_C_COMPILER_ID MATCHES "GNU" AND CMAKE_C_COMPILER_VERSION VERSION_LESS "4.9")
+  SET(HAVE_C_THREAD_LOCAL 0)
+ELSE()
+  SET(HAVE_C_THREAD_LOCAL 1)
+ENDIF()
+
 #native password
 REGISTER_PLUGIN(TARGET mysql_native_password
                 TYPE MARIADB_CLIENT_PLUGIN_AUTH
@@ -62,6 +69,12 @@ IF(CRYPTO_PLUGIN)
                 INCLUDES ${REF10_DIR}
                 LIBRARIES ${CRYPT_LIBS}
                 COMPILE_OPTIONS -DMYSQL_CLIENT=1)
+  SET_PROPERTY(TARGET client_ed25519 PROPERTY C_STANDARD 11)
+
+  IF(HAVE_C_THREAD_LOCAL)
+    TARGET_COMPILE_DEFINITIONS(client_ed25519 PRIVATE -DHAVE_THREAD_LOCAL)
+  ENDIF()
+
   IF(MSVC)
      # Silence conversion (integer truncation) warnings from reference code
      SET_SOURCE_FILES_PROPERTIES(${REF10_SOURCES} PROPERTY COMPILE_FLAGS "-DMYSQL_CLIENT=1 /wd4244 /wd4146")
diff --git a/plugins/auth/ed25519.c b/plugins/auth/ed25519.c
index ff2f39a5..a47a5049 100644
--- a/plugins/auth/ed25519.c
+++ b/plugins/auth/ed25519.c
@@ -88,15 +88,20 @@ struct st_mysql_client_plugin_AUTHENTICATION _mysql_client_plugin_declaration_ =
   auth_ed25519_hash
 };
 
+#ifdef HAVE_THREAD_LOCAL
+/* pk will be used in the future auth_ed25519_hash() call, after the authentication */
+static _Thread_local unsigned char pk[CRYPTO_PUBLICKEYBYTES];
+#endif
 
 static int auth_ed25519_client(MYSQL_PLUGIN_VIO *vio, MYSQL *mysql)
 {
   unsigned char *packet,
-                signature[CRYPTO_BYTES + NONCE_BYTES],
-                pk[CRYPTO_PUBLICKEYBYTES];
+                signature[CRYPTO_BYTES + NONCE_BYTES];
+#ifndef HAVE_THREAD_LOCAL
+  unsigned char pk[CRYPTO_PUBLICKEYBYTES];
+#endif
   unsigned long long pkt_len;
   size_t pwlen= strlen(mysql->passwd);
-  char *newpw;
 
   /*
      Step 1: Server sends nonce
@@ -117,26 +122,27 @@ static int auth_ed25519_client(MYSQL_PLUGIN_VIO *vio, MYSQL *mysql)
   if (vio->write_packet(vio, signature, CRYPTO_BYTES))
     return CR_ERROR;
 
-  /* save pk for the future auth_ed25519_hash() call */
-  if ((newpw= realloc(mysql->passwd, pwlen + 1 + sizeof(pk))))
-  {
-    memcpy(newpw + pwlen + 1, pk, sizeof(pk));
-    mysql->passwd= newpw;
-  }
-
   return CR_OK;
 }
 /* }}} */
 
 /* {{{ static int auth_ed25519_hash */
-static int auth_ed25519_hash(MYSQL *mysql, unsigned char *out, size_t *outlen)
+static int auth_ed25519_hash(MYSQL *mysql __attribute__((unused)),
+                             unsigned char *out, size_t *outlen)
 {
+#ifndef HAVE_THREAD_LOCAL
+  unsigned char pk[CRYPTO_PUBLICKEYBYTES];
+#endif
   if (*outlen < CRYPTO_PUBLICKEYBYTES)
     return 1;
   *outlen= CRYPTO_PUBLICKEYBYTES;
 
+#ifndef HAVE_THREAD_LOCAL
+  crypto_sign_keypair(pk, (unsigned char*)mysql->passwd, strlen(mysql->passwd));
+#endif
+
   /* use the cached value */
-  memcpy(out, mysql->passwd + strlen(mysql->passwd) + 1, CRYPTO_PUBLICKEYBYTES);
+  memcpy(out, pk, CRYPTO_PUBLICKEYBYTES);
   return 0;
 }
 /* }}} */
diff --git a/unittest/libmariadb/bulk1.c b/unittest/libmariadb/bulk1.c
index 2b00bdde..888904d5 100644
--- a/unittest/libmariadb/bulk1.c
+++ b/unittest/libmariadb/bulk1.c
@@ -1125,8 +1125,8 @@ static int bulk_with_unit_result_insert(MYSQL *my)
   check_stmt_rc(rc, stmt);
 
   /* allocate memory */
-  buffer= calloc(TEST_ARRAY_SIZE, sizeof(char *));
-  lengths= (unsigned long *)calloc(sizeof(long), TEST_ARRAY_SIZE);
+  buffer= calloc(TEST_ARRAY_SIZE, sizeof *buffer);
+  lengths= calloc(TEST_ARRAY_SIZE, sizeof *lengths);
 
   for (i=0; i < TEST_ARRAY_SIZE; i++)
   {
@@ -1251,7 +1251,7 @@ static int bulk_with_unit_result_delete(MYSQL *my)
   rc= mysql_stmt_attr_set(stmt, STMT_ATTR_ARRAY_SIZE, &array_size);
   check_stmt_rc(rc, stmt);
 
-  vals= (unsigned int *)calloc(sizeof(int), 5);
+  vals= calloc(5, sizeof *vals);
   memset(bind, 0, sizeof(MYSQL_BIND) * 1);
   bind[0].buffer_type= MYSQL_TYPE_LONG;
   bind[0].buffer= vals;
@@ -1359,7 +1359,7 @@ static int bulk_with_unit_result_update(MYSQL *my)
   rc= mysql_stmt_attr_set(stmt, STMT_ATTR_ARRAY_SIZE, &array_size);
   check_stmt_rc(rc, stmt);
 
-  vals= (unsigned int *)calloc(sizeof(int), 5);
+  vals= calloc(5, sizeof *vals);
   memset(bind, 0, sizeof(MYSQL_BIND) * 1);
   bind[0].buffer_type= MYSQL_TYPE_LONG;
   bind[0].buffer= vals;