diff --git a/third_party/CMakeLists.txt b/third_party/CMakeLists.txt
index 06be77c1..c7acb1fa 100644
--- a/third_party/CMakeLists.txt
+++ b/third_party/CMakeLists.txt
@@ -6,5 +6,9 @@ add_subdirectory(stb)
 if(USE_EXTERNAL_PLOG)
   find_package(plog REQUIRED)
 else()
+  if (NOT EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/plog/CMakeLists.txt)
+    message(FATAL_ERROR "plog third-party directory could not be found. "
+      "Please run 'submodule update --init --recursive' in the source directory.")
+  endif()
   add_subdirectory(plog)
 endif()