diff --git a/include/BoostInstall.cmake b/include/BoostInstall.cmake
index 1127c6f..bdeb7d7 100644
--- a/include/BoostInstall.cmake
+++ b/include/BoostInstall.cmake
@@ -320,6 +320,8 @@ function(boost_install_target)
 
   install(EXPORT ${LIB}-targets DESTINATION "${CONFIG_INSTALL_DIR}" NAMESPACE Boost:: FILE ${LIB}-targets.cmake)
 
+  set_target_properties(${LIB} PROPERTIES _boost_is_installed ON)
+
   set(CONFIG_FILE_NAME "${CMAKE_CURRENT_BINARY_DIR}/tmpinst/${LIB}-config.cmake")
   set(CONFIG_FILE_CONTENTS "# Generated by BoostInstall.cmake for ${LIB}-${__VERSION}\n\n")
 
diff --git a/include/BoostRoot.cmake b/include/BoostRoot.cmake
index bd7f8be..ad37410 100644
--- a/include/BoostRoot.cmake
+++ b/include/BoostRoot.cmake
@@ -182,6 +182,11 @@ function(__boost_auto_install __boost_lib)
 
     if(TARGET "Boost::${__boost_lib_target}" AND TARGET "boost_${__boost_lib_target}")
 
+      get_target_property(is_installed "boost_${__boost_lib_target}" _boost_is_installed)
+      if(is_installed)
+        return() # Ignore libraries for which boost_install was already called
+      endif()
+
       get_target_property(__boost_lib_incdir "boost_${__boost_lib_target}" INTERFACE_INCLUDE_DIRECTORIES)
 
       set(incdir "${BOOST_SUPERPROJECT_SOURCE_DIR}/libs/${__boost_lib}/include")