diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 1779bcd9ad..8e7ffd8342 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -467,7 +467,7 @@ endif ()
 
 add_custom_target(
     standard_lib ALL
-    COMMAND make -j4 -e LEAN="${LEAN_SOURCE_DIR}/../bin/lean" "${LEAN_EXTRA_MAKE_OPTS}"
+    COMMAND make -j4 -e "LEAN=${LEAN_SOURCE_DIR}/../bin/lean ${LEAN_EXTRA_MAKE_OPTS}"
     DEPENDS bin_lean
     WORKING_DIRECTORY "${LEAN_SOURCE_DIR}/../library"
     )