diff --git a/platformio/builder/tools/piolib.py b/platformio/builder/tools/piolib.py
index e728216e..bab464ba 100644
--- a/platformio/builder/tools/piolib.py
+++ b/platformio/builder/tools/piolib.py
@@ -333,7 +333,7 @@ class LibBuilderBase:
             LibBuilderBase._INCLUDE_DIRS_CACHE = [
                 self.env.Dir(d)
                 for d in ProjectAsLibBuilder(
-                    self.envorigin, "$PROJECT_DIR"
+                    self.envorigin, "$PROJECT_DIR", export_projenv=False
                 ).get_include_dirs()
             ]
             for lb in self.env.GetLibBuilders():
@@ -862,10 +862,15 @@ class PlatformIOLibBuilder(LibBuilderBase):
 
 class ProjectAsLibBuilder(LibBuilderBase):
     def __init__(self, env, *args, **kwargs):
+        export_projenv = kwargs.get("export_projenv", True)
+        if "export_projenv" in kwargs:
+            del kwargs["export_projenv"]
         # backup original value, will be reset in base.__init__
         project_src_filter = env.get("SRC_FILTER")
         super().__init__(env, *args, **kwargs)
         self.env["SRC_FILTER"] = project_src_filter
+        if export_projenv:
+            env.Export(dict(projenv=self.env))
 
     @property
     def include_dir(self):
@@ -1130,7 +1135,6 @@ def ConfigureProjectLibBuilder(env):
                 _print_deps_tree(lb, level + 1)
 
     project = ProjectAsLibBuilder(env, "$PROJECT_DIR")
-    env.Export(dict(projenv=project.env))
 
     if "test" in env.GetBuildType():
         project.env.ConfigureTestTarget()