diff --git a/lib/mayaUsd/CMakeLists.txt b/lib/mayaUsd/CMakeLists.txt
index fcca8adf00..f792b1fb68 100644
--- a/lib/mayaUsd/CMakeLists.txt
+++ b/lib/mayaUsd/CMakeLists.txt
@@ -20,8 +20,8 @@ add_library(${PROJECT_NAME} SHARED)
 #------------------------------------------------------------------------------
 # modules and definitions
 #------------------------------------------------------------------------------
-if(NOT DEFINED BOOST_ROOT)
-    set(BOOST_ROOT ${PXR_USD_LOCATION})
+if(NOT DEFINED ENV{BOOST_ROOT})
+    set(ENV{BOOST_ROOT} ${PXR_USD_LOCATION})
 endif()
 if(MAYAUSD_DEFINE_BOOST_DEBUG_PYTHON_FLAG)
     set(Boost_USE_DEBUG_PYTHON ON)
diff --git a/plugin/al/CMakeLists.txt b/plugin/al/CMakeLists.txt
index 1cfe615dd6..3b6cb133ae 100644
--- a/plugin/al/CMakeLists.txt
+++ b/plugin/al/CMakeLists.txt
@@ -10,8 +10,8 @@ endif()
 set(NEED_BOOST_FILESYSTEM ON)
 set(CMAKE_VERBOSE_MAKEFILE OFF)
 set(CMAKE_INCLUDE_CURRENT_DIR ON)
-if(NOT DEFINED BOOST_ROOT)
-    set(BOOST_ROOT ${PXR_USD_LOCATION})
+if(NOT DEFINED ENV{BOOST_ROOT})
+    set(ENV{BOOST_ROOT} ${PXR_USD_LOCATION})
 endif()
 
 set(INSTALL_DIR_SUFFIX plugin/al)