diff --git a/lib/mysql_connection.cpp b/lib/mysql_connection.cpp
index bdb917dd67..48ce4a73b2 100644
--- a/lib/mysql_connection.cpp
+++ b/lib/mysql_connection.cpp
@@ -387,6 +387,7 @@ MySQL_Connection::~MySQL_Connection() {
 		if (variables[i].value) {
 			free(variables[i].value);
 			variables[i].value = NULL;
+			var_hash[i] = 0;
 		}
 	}
 
@@ -2264,6 +2265,7 @@ void MySQL_Connection::reset() {
 		if (variables[i].value) {
 			free(variables[i].value);
 			variables[i].value = NULL;
+			var_hash[i] = 0;
 		}
 	}
 
diff --git a/test/tap/tests/Makefile b/test/tap/tests/Makefile
index 43124fcde0..52d866f1db 100644
--- a/test/tap/tests/Makefile
+++ b/test/tap/tests/Makefile
@@ -75,13 +75,13 @@ all: tests
 
 .PHONY: clean
 clean:
-	rm -f basic-t set_character_set-t charset_unsigned_int-t select_config_file-t sqlite3-t galera_1_timeout_count galera_2_timeout_no_count aurora test_set_character_results-t test_ps_large_result-t set_testing-t test_firewall-t || true
+	rm -f basic-t set_character_set-t charset_unsigned_int-t select_config_file-t sqlite3-t galera_1_timeout_count galera_2_timeout_no_count aurora test_set_character_results-t test_ps_large_result-t set_testing-t test_firewall-t test_default_value_transaction_isolation-t || true
 
 OPT=-O2
 
-SRC=basic-t.cpp set_character_set-t.cpp charset_unsigned_int-t.cpp select_config_file-t.cpp sqlite3-t.cpp  galera_1_timeout_count.cpp galera_2_timeout_no_count.cpp aurora.cpp test_set_character_results-t.cpp test_ps_large_result-t.cpp set_testing-t.cpp test_firewall-t.cpp
+SRC=basic-t.cpp set_character_set-t.cpp charset_unsigned_int-t.cpp select_config_file-t.cpp sqlite3-t.cpp  galera_1_timeout_count.cpp galera_2_timeout_no_count.cpp aurora.cpp test_set_character_results-t.cpp test_ps_large_result-t.cpp set_testing-t.cpp test_firewall-t.cpp test_default_value_transaction_isolation-t.cpp
 
-tests: basic-t set_character_set-t charset_unsigned_int-t select_config_file-t sqlite3-t test_set_character_results-t test_ps_large_result-t set_testing-t test_firewall-t
+tests: basic-t set_character_set-t charset_unsigned_int-t select_config_file-t sqlite3-t test_set_character_results-t test_ps_large_result-t set_testing-t test_firewall-t test_default_value_transaction_isolation-t
 testgalera: galera_1_timeout_count galera_2_timeout_no_count
 testaurora: aurora
 
@@ -120,3 +120,6 @@ aurora: aurora.cpp $(TAP_LIBDIR)/libtap.a
 
 set_testing-t: set_testing-t.cpp $(TAP_LIBDIR)/libtap.a
 	g++ set_testing-t.cpp -Wall $(INCLUDEDIRS) $(LDIRS) $(OPT) -std=c++11 $(MYLIBS) -ltap -pthread -O0 -ggdb -ldl -lssl -lcrypto -o set_testing-t
+
+test_default_value_transaction_isolation-t: test_default_value_transaction_isolation-t.cpp $(TAP_LIBDIR)/libtap.a
+	g++ test_default_value_transaction_isolation-t.cpp -Wall $(INCLUDEDIRS) $(LDIRS) $(OPT) -std=c++11 $(MYLIBS) -ltap -pthread -O0 -ggdb -ldl -lssl -lcrypto -o test_default_value_transaction_isolation-t
diff --git a/test/tap/tests/test_default_value_transaction_isolation-t.cpp b/test/tap/tests/test_default_value_transaction_isolation-t.cpp
new file mode 100644
index 0000000000..cca5d20806
--- /dev/null
+++ b/test/tap/tests/test_default_value_transaction_isolation-t.cpp
@@ -0,0 +1,91 @@
+#include <cstdlib>
+#include <cstdio>
+#include <cstring>
+#include <unistd.h>
+
+#include <string>
+#include <sstream>
+#include <mysql.h>
+
+#include "tap.h"
+#include "command_line.h"
+#include "utils.h"
+
+int main(int argc, char** argv) {
+	CommandLine cl;
+
+	if(cl.getEnv())
+		return exit_status();
+
+	plan(3);
+	diag("Testing default value for session varable transaction isolation");
+
+	MYSQL* mysqladmin = mysql_init(NULL);
+	if (!mysqladmin)
+		return exit_status();
+
+	if (!mysql_real_connect(mysqladmin, cl.host, cl.admin_username, cl.admin_password, NULL, cl.admin_port, NULL, 0)) {
+	    fprintf(stderr, "File %s, line %d, Error: %s\n",
+	              __FILE__, __LINE__, mysql_error(mysqladmin));
+		return exit_status();
+	}
+
+	// Set default non-existing value for transaction isolation level
+	MYSQL_QUERY(mysqladmin, "set mysql-default_isolation_level='non-existing-value-1'");
+	MYSQL_QUERY(mysqladmin, "load mysql variables to runtime");
+
+	MYSQL* mysql_1 = mysql_init(NULL);
+	if (!mysql_1)
+		return exit_status();
+
+	if (!mysql_real_connect(mysql_1, cl.host, cl.username, cl.password, NULL, cl.port, NULL, 0)) {
+	    fprintf(stderr, "Failed to connect to database: Error: %s\n",
+	              mysql_error(mysql_1));
+		return exit_status();
+	}
+	MYSQL_QUERY(mysql_1, "select 1");
+	MYSQL_RES* result = mysql_store_result(mysql_1);
+	ok(mysql_num_rows(result) == 1, "Select statement should be executed on connection 1");
+	mysql_free_result(result);
+
+	MYSQL* mysql_2 = mysql_init(NULL);
+	if (!mysql_2)
+		return exit_status();
+
+	if (!mysql_real_connect(mysql_2, cl.host, cl.username, cl.password, NULL, cl.port, NULL, 0)) {
+	    fprintf(stderr, "Failed to connect to database: Error: %s\n",
+	              mysql_error(mysql_2));
+		return exit_status();
+	}
+	MYSQL_QUERY(mysql_2, "select 1");
+	result = mysql_store_result(mysql_2);
+	ok(mysql_num_rows(result) == 1, "Select statement should be executed on connection 1");
+	mysql_free_result(result);
+
+	// Change default non-existing value for transaction isolation level
+	MYSQL_QUERY(mysqladmin, "set mysql-default_isolation_level='non-existing-value-2'");
+	MYSQL_QUERY(mysqladmin, "load mysql variables to runtime");
+
+	// Try third connection with different default value of the session variable
+	MYSQL* mysql_3 = mysql_init(NULL);
+	if (!mysql_3)
+		return exit_status();
+
+	if (!mysql_real_connect(mysql_3, cl.host, cl.username, cl.password, NULL, cl.port, NULL, 0)) {
+	    fprintf(stderr, "Failed to connect to database: Error: %s\n",
+	              mysql_error(mysql_3));
+		return exit_status();
+	}
+	MYSQL_QUERY(mysql_3, "select 1");
+	result = mysql_store_result(mysql_3);
+	ok(mysql_num_rows(result) == 1, "Select statement should be executed on connection 1");
+	mysql_free_result(result);
+	
+	mysql_close(mysql_3);
+	mysql_close(mysql_2);
+	mysql_close(mysql_1);
+	mysql_close(mysqladmin);
+
+	return exit_status();
+}
+