--- CMakeLists.txt
+++ CMakeLists.txt
@@ -41,9 +41,9 @@
 # when absl is included as subproject (i.e. using add_subdirectory(abseil-cpp))
 # in the source tree of a project that uses it, install rules are disabled.
 if(NOT "^${CMAKE_SOURCE_DIR}$" STREQUAL "^${PROJECT_SOURCE_DIR}$")
-  set(ABSL_ENABLE_INSTALL FALSE)
+  option(ABSL_ENABLE_INSTALL "Enable install rule" OFF)
 else()
-  set(ABSL_ENABLE_INSTALL TRUE)
+  option(ABSL_ENABLE_INSTALL "Enable install rule" ON)
 endif()
 
 list(APPEND CMAKE_MODULE_PATH