diff --git a/CMakeLists.txt b/CMakeLists.txt
index 6f0786915e..1e62938646 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -140,6 +140,8 @@ if(MSVC)
             if(NOT HAVE_PTHREAD_H)
                 message(FATAL_ERROR "Could not find pthreads.")
             endif()
+            unset(PThreads_LIBRARIES)
+            unset(PThreads_INCLUDE_DIRS)
         endif()
     endif()
     set(FLINT_USES_PTHREAD ON CACHE BOOL "Use POSIX Threads.")