diff --git a/cmake/KF5AuthMacros.cmake b/cmake/KF5AuthMacros.cmake
index ab0b30a..50b7ad1 100644
--- a/cmake/KF5AuthMacros.cmake
+++ b/cmake/KF5AuthMacros.cmake
@@ -18,7 +18,7 @@ function(KAUTH_INSTALL_HELPER_FILES HELPER_TARGET HELPER_ID HELPER_USER)
         install(FILES ${CMAKE_CURRENT_BINARY_DIR}/${HELPER_ID}.conf
                 DESTINATION ${SYSCONF_INSTALL_DIR}/dbus-1/system.d/)
 
-        if(IS_ABSOLUTE KAUTH_HELPER_INSTALL_DIR)
+        if(IS_ABSOLUTE ${KAUTH_HELPER_INSTALL_DIR})
             set(KAUTH_HELPER_INSTALL_ABSOLUTE_DIR ${KAUTH_HELPER_INSTALL_DIR})
         else()
             set(KAUTH_HELPER_INSTALL_ABSOLUTE_DIR "${CMAKE_INSTALL_PREFIX}/${KAUTH_HELPER_INSTALL_DIR}")