diff --git a/setup.py b/setup.py
index 341ab5f2..e649e43e 100644
--- a/setup.py
+++ b/setup.py
@@ -169,11 +169,7 @@ class CMakeBuild(build_ext):
                     env['_PYTHON_HOST_PLATFORM'] = re.sub(r'macosx-[0-9]+\.[0-9]+-(.+)', r'macosx-10.9-\1', util.get_platform())
 
             # Specify how many threads to use when building, depending on available memory
-            max_threads = multiprocessing.cpu_count()
-            num_threads = (freeMemory // 2000)
-            num_threads = min(num_threads, max_threads)
-            if num_threads <= 0:
-                num_threads = 1
+            num_threads = int(os.environ['NIX_BUILD_CORES'])
             build_args += ['--', '-j' + str(num_threads)]
             cmake_args += ['-DHUNTER_JOBS_NUMBER=' + str(num_threads)]
 
@@ -187,8 +183,8 @@ class CMakeBuild(build_ext):
             os.makedirs(self.build_temp)
 
         # Configure and build
-        subprocess.check_call(['cmake', ext.sourcedir] + cmake_args, cwd=self.build_temp, env=env)
-        subprocess.check_call(['cmake', '--build', '.'] + build_args, cwd=self.build_temp, env=env)
+        subprocess.check_call(['cmake', ext.sourcedir] + cmake_args, env=env)
+        subprocess.check_call(['cmake', '--build', '.'] + build_args, env=env)
 
 setup(
     name=MODULE_NAME,