diff --git a/python/CMakeLists.txt b/python/CMakeLists.txt
index 65593c5..56e5118 100644
--- a/python/CMakeLists.txt
+++ b/python/CMakeLists.txt
@@ -23,7 +23,7 @@ add_custom_command(
 add_custom_target(PythonInstall DEPENDS "${WRAP_FILE}"  "${CMAKE_CURRENT_SOURCE_DIR}/setup.py")
 set(NN_PLUGIN_HEADER_DIR "${CMAKE_SOURCE_DIR}/openmmapi/include")
 set(NN_PLUGIN_LIBRARY_DIR "${CMAKE_BINARY_DIR}")
-set(EXTENSION_CXX_STANDARD ${CMAKE_CXX_STANDARD})
+set(EXTENSION_CXX_STANDARD "${CMAKE_CXX_STANDARD}")
 configure_file(${CMAKE_CURRENT_SOURCE_DIR}/setup.py ${CMAKE_CURRENT_BINARY_DIR}/setup.py)
 add_custom_command(TARGET PythonInstall
     COMMAND "${PYTHON_EXECUTABLE}" -m pip install .