diff --git a/port/libusb/CMakeLists.txt b/port/libusb/CMakeLists.txt
index a1d783228..748a1bb54 100644
--- a/port/libusb/CMakeLists.txt
+++ b/port/libusb/CMakeLists.txt
@@ -12,10 +12,10 @@ link_libraries( usb-1.0 )
 # extra compiler warnings
 if ("${CMAKE_C_COMPILER_ID}" MATCHES ".*Clang.*")
 	# using Clang
-	SET(CMAKE_C_FLAGS  "${CMAKE_C_FLAGS} -Wunused-variable -Wswitch-default")
+	SET(CMAKE_C_FLAGS  "${CMAKE_C_FLAGS} -Wunused-variable -Wswitch-default -Werror")
 elseif ("${CMAKE_C_COMPILER_ID}" STREQUAL "GNU")
 	# using GCC
-	SET(CMAKE_C_FLAGS  "${CMAKE_C_FLAGS} -Wunused-but-set-variable -Wunused-variable -Wswitch-default")
+	SET(CMAKE_C_FLAGS  "${CMAKE_C_FLAGS} -Wunused-but-set-variable -Wunused-variable -Wswitch-default -Werror")
 elseif ("${CMAKE_C_COMPILER_ID}" STREQUAL "Intel")
 	# using Intel C++
 elseif ("${CMAKE_C_COMPILER_ID}" STREQUAL "MSVC")