diff --git a/python/CMakeLists.txt b/python/CMakeLists.txt
index a8d80b0c1..c57487c72 100644
--- a/python/CMakeLists.txt
+++ b/python/CMakeLists.txt
@@ -1,2 +1,3 @@
-add_subdirectory( pybind11 )
-
+if(NOT TARGET pybind11)
+  add_subdirectory( pybind11 )
+endif()