diff --git a/CI/travis/lib.sh b/CI/travis/lib.sh
index bfea28e5c..19bcf15b3 100644
--- a/CI/travis/lib.sh
+++ b/CI/travis/lib.sh
@@ -26,7 +26,7 @@ INSIDE_DOCKER_BUILD_DIR=/docker_build_dir
 #
 # If these nothing should be passed, then clear or
 #'unset INSIDE_DOCKER_TRAVIS_CI_ENV' after this script is included
-INSIDE_DOCKER_TRAVIS_CI_ENV="TRAVIS TRAVIS_COMMIT TRAVIS_PULL_REQUEST OS_TYPE OS_VERSION ARTIFACTNAME"
+INSIDE_DOCKER_TRAVIS_CI_ENV="TF_BUILD TRAVIS TRAVIS_COMMIT TRAVIS_PULL_REQUEST OS_TYPE OS_VERSION ARTIFACTNAME"
 
 COMMON_SCRIPTS="inside_docker.sh"
 
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 6b866b48e..a10470485 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -170,8 +170,12 @@ endif()
 # make sure all check_symbol_exists are before this point, otherwise they fail
 # on some versions of compilers
 if (MSVC)
-	if(DEFINED ENV{CI} AND DEFINED ENV{APPVEYOR})
-		message(STATUS "Running in an AppVeyor environment, setting -Werror")
+	# why can't different CIs use the same flags?
+	# Travis CI      : CI=True & TRAVIS=True
+	# Appveyor       : CI=True & APPVEYOR=True
+	# Azure Pipelines: TF_BUILD=True
+	if(DEFINED ENV{TF_BUILD} OR (DEFINED ENV{CI} AND DEFINED ENV{APPVEYOR}))
+		message(STATUS "Running in an Azure or AppVeyor environment, setting -Werror")
 		add_compile_options(/WX)
 	endif()
 elseif (CMAKE_COMPILER_IS_GNUCC OR CMAKE_C_COMPILER_ID STREQUAL "Clang")
@@ -181,10 +185,13 @@ elseif (CMAKE_COMPILER_IS_GNUCC OR CMAKE_C_COMPILER_ID STREQUAL "Clang")
 		SET(CMAKE_EXE_LINKER_FLAGS  "${CMAKE_EXE_LINKER_FLAGS} -fprofile-arcs -ftest-coverage")
 		SET(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS}  -fprofile-arcs -ftest-coverage")
 	endif()
-	if(DEFINED ENV{CI} AND (DEFINED ENV{TRAVIS} OR DEFINED ENV{APPVEYOR}))
-		message(STATUS "Running in CI environment (Travis or AppVeyor), setting -Werror")
+	if(DEFINED ENV{TF_BUILD} OR (DEFINED ENV{CI} AND (DEFINED ENV{TRAVIS} OR DEFINED ENV{APPVEYOR})))
+		message(STATUS "Running in CI environment (Azure, Travis or AppVeyor), setting -Werror")
 		set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Werror")
 	endif()
+else()
+	message(STATUS "Unknown compiler ${CMAKE_C_COMPILER_ID}")
+	message(STATUS "GCC ${CMAKE_COMPILER_IS_GNUCC}")
 endif()
 
 IF(${CMAKE_SYSTEM_NAME} MATCHES "Linux")
diff --git a/examples/CMakeLists.txt b/examples/CMakeLists.txt
index 8179905ba..961e26bde 100644
--- a/examples/CMakeLists.txt
+++ b/examples/CMakeLists.txt
@@ -69,7 +69,10 @@ if (PTHREAD_LIBRARIES
     set(TEMP1 ${CMAKE_REQUIRED_INCLUDES})
     list(APPEND CMAKE_REQUIRED_LIBRARIES ${CURSES_LIBRARY} ${CDK_LIBRARY})
     list(APPEND CMAKE_REQUIRED_INCLUDES ${LIBCKD_INCLUDE_DIR})
+    set(TMP_FLAGS "${CMAKE_C_FLAGS}")
+    set(CMAKE_C_FLAGS "")
     check_symbol_exists(CDK_CSTRING2 "cdk.h" HAS_CDK_CSTRING2)
+    set(CMAKE_C_FLAGS "${TMP_FLAGS}")
     set(CMAKE_REQUIRED_LIBRARIES ${TEMP})
     set(CMAKE_REQUIRED_INCLUDES ${TEMP1})
 endif()
diff --git a/iiod/CMakeLists.txt b/iiod/CMakeLists.txt
index b144493ff..3d22ff5c0 100644
--- a/iiod/CMakeLists.txt
+++ b/iiod/CMakeLists.txt
@@ -15,7 +15,10 @@ include_directories(${CMAKE_CURRENT_SOURCE_DIR})
 include(CheckSymbolExists)
 set(CMAKE_REQUIRED_LIBRARIES ${PTHREAD_LIBRARIES})
 set(CMAKE_REQUIRED_DEFINITIONS -D_GNU_SOURCE)
+set(TMP_FLAGS "${CMAKE_C_FLAGS}")
+set(CMAKE_C_FLAGS "")
 check_symbol_exists(pthread_setname_np "pthread.h" HAS_PTHREAD_SETNAME_NP)
+set(CMAKE_C_FLAGS "${TMP_FLAGS}")
 set(CMAKE_REQUIRED_LIBRARIES)
 set(CMAKE_REQUIRED_DEFINITIONS)