diff --git a/cmake/app/boilerplate.cmake b/cmake/app/boilerplate.cmake
index b0920b1d955..73e5cc48de8 100644
--- a/cmake/app/boilerplate.cmake
+++ b/cmake/app/boilerplate.cmake
@@ -28,6 +28,14 @@ cmake_policy(SET CMP0002 NEW)
 # CMP0079: "target_link_libraries() allows use with targets in other directories"
 cmake_policy(SET CMP0079 OLD)
 
+# Error-out if 'project' has been invoked to avoid obscure user
+# errors.
+if(DEFINED CMAKE_PROJECT_NAME)
+  message(FATAL_ERROR
+    "'project()' was called before boilerplate.cmake was included, this is not supported."
+    )
+endif()
+
 define_property(GLOBAL PROPERTY ZEPHYR_LIBS
     BRIEF_DOCS "Global list of all Zephyr CMake libs that should be linked in"
     FULL_DOCS  "Global list of all Zephyr CMake libs that should be linked in.