diff --git a/setup.py b/setup.py
index 7db697f..bd30b12 100644
--- a/setup.py
+++ b/setup.py
@@ -33,6 +33,10 @@ def run(self):
 
     def build_extension(self, ext):
         extdir = os.path.abspath(os.path.dirname(self.get_ext_fullpath(ext.name)))
+        # required for auto-detection of auxiliary "native" libs
+        if not extdir.endswith(os.path.sep):
+            extdir += os.path.sep
+
         cmake_args = ['-DCMAKE_LIBRARY_OUTPUT_DIRECTORY=' + extdir,
                       '-DPYTHON_EXECUTABLE=' + sys.executable]