diff --git a/.circleci/config.yml b/.circleci/config.yml
index 633fe458..84eb17f0 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -520,38 +520,6 @@ jobs:
       - run: ldd /opt/fastnetmon/fastnetmon_client
       - run: ldd /opt/fastnetmon/fastnetmon_api_client
       - run: /opt/fastnetmon/fastnetmon --configuration_check
-  centos6:
-    docker:
-      - image: centos:centos6.9
-    steps:
-      - checkout
-      - run: yum install -y perl wget
-      - run:
-          name: install_required_packages
-          no_output_timeout: 20m
-          command: perl src/fastnetmon_build.pl --install_dependency_packages_only --source_build
-      - restore_cache:
-          keys:
-            - "{{ .Environment.CIRCLE_JOB }}_dependencies_27_05_2020"
-      - run:
-          name: install_dependencies
-          no_output_timeout: 40m
-          command: perl src/fastnetmon_build.pl --use-git-master --source_build
-      - run:
-          name: collect_debug
-          command: cat /tmp/fastnetmon_install.log
-          when: on_fail
-      - save_cache:
-          key: "{{ .Environment.CIRCLE_JOB }}_dependencies_27_05_2020"
-          paths:
-            - /opt
-            - /usr/include/linux/pf_ring.h
-      - run: cd src; mkdir -p build; cd build; cmake ..; make
-      - run: ldd /opt/fastnetmon/fastnetmon
-      - run: ldd /opt/fastnetmon/fastnetmon_client
-      - run: /opt/fastnetmon/fastnetmon --configuration_check
-      - store_artifacts:
-          path: /tmp/fastnetmon_install.log
   centos6_all_libs:
     docker:
       - image: centos:centos6.9
@@ -769,7 +737,6 @@ workflows:
       - ubuntu1804_all_libs
       - ubuntu2004
       - ubuntu2004_all_libs
-      - centos6
       - centos6_all_libs
       - centos7
       - centos7_all_libs
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 8cbf95a2..d42eb389 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -23,6 +23,9 @@ include(CheckLibraryExists)
 set (FASTNETMON_VERSION_MAJOR 1)
 set (FASTNETMON_VERSION_MINOR 1)
 
+set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} --std=c++11")
+set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} --std=c++11")
+
 set(CMAKE_INSTALL_SYSTEMD_SERVICEDIR "/lib/systemd/system"
   CACHE PATH "Location for systemd service files")