diff --git a/build_files/cmake/platform/platform_unix.cmake b/build_files/cmake/platform/platform_unix.cmake
index 9e737a8152c..68f4b6a36ca 100644
--- a/build_files/cmake/platform/platform_unix.cmake
+++ b/build_files/cmake/platform/platform_unix.cmake
@@ -37,21 +37,22 @@ else()
     unset(LIBDIR_GLIBC228_ABI)
   endif()
 
-  if(NOT DEFINED LIBDIR OR NOT (EXISTS ${LIBDIR}))
+  if(NOT DEFINED LIBDIR)
+    set(LIBDIR "")  # Suppress undefined warnings, allow printing even if empty.
+  endif()
+  if((LIBDIR STREQUAL "") OR (NOT (EXISTS "${LIBDIR}")))
     if(WITH_STRICT_BUILD_OPTIONS)
       message(SEND_ERROR
-        "Unable to find LIBDIR: ${LIBDIR}. "
+        "Unable to find LIBDIR: \"${LIBDIR}\". "
         "WITH_LIBS_PRECOMPILED needs to be able to find the LIBDIR for the precompiled libraries."
       )
     else()
       message(STATUS
-        "Unable to find LIBDIR: ${LIBDIR}. system libraries may be used "
+        "Unable to find LIBDIR: \"${LIBDIR}\". system libraries may be used "
         "(disable WITH_LIBS_PRECOMPILED to suppress this message)."
       )
     endif()
-    if(DEFINED LIBDIR)
-      unset(LIBDIR)
-    endif()
+    unset(LIBDIR)
     set(WITH_LIBS_PRECOMPILED OFF)
   endif()
 endif()