diff --git a/CMakeLists.txt b/CMakeLists.txt
index 9fe5837..1efe6bc 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -59,12 +59,12 @@ if(CMAKE_SYSTEM_NAME MATCHES "Linux")
 	set(PLATFORM_LIBS ${PLATFORM_LIBS} pthread)
 endif()
 
-if(CMAKE_SYSTEM_NAME MATCHES "MINGW")
-	set(BUILD_NC false)
-endif()
-
-if(WIN32)
+if(WIN32 OR (CMAKE_SYSTEM_NAME MATCHES "MINGW"))
 	set(BUILD_NC false)
+	add_definitions(-D_GNU_SOURCE)
+	add_definitions(-D_POSIX)
+	add_definitions(-D_POSIX_SOURCE)
+	add_definitions(-D__USE_MINGW_ANSI_STDIO)
 endif()
 
 set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -O2 -Wall")
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 2a9389d..d3113ab 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -25,7 +25,7 @@ add_test(aes_wrap aes_wrap)
 
 # arc4randomforktest
 # Windows/mingw does not have fork, but Cygwin does.
-if(NOT CMAKE_HOST_WIN32 AND NOT CMAKE_SYSTEM_NAME MATCHES "MINGW")
+if(NOT (WIN32 OR (CMAKE_SYSTEM_NAME MATCHES "MINGW")))
 	add_executable(arc4randomforktest arc4randomforktest.c)
 	target_link_libraries(arc4randomforktest ${OPENSSL_LIBS})
 	add_test(arc4randomforktest ${CMAKE_CURRENT_SOURCE_DIR}/arc4randomforktest.sh)