diff --git a/HISTORY.rst b/HISTORY.rst
index dd23ed95..f987612a 100644
--- a/HISTORY.rst
+++ b/HISTORY.rst
@@ -19,6 +19,9 @@ PlatformIO 3.0
 * `PIO Account <http://docs.platformio.org/en/latest/userguide/account/index.html>`__
   and `PLATFORMIO_AUTH_TOKEN <http://docs.platformio.org/en/latest/envvars.html#envvar-PLATFORMIO_AUTH_TOKEN>`__
   environment variable for CI systems
+* Refactored `Library Dependency Finder (LDF) <http://docs.platformio.org/en/stable/librarymanager/ldf.html>`__
+  C/C++ Preprocessor for conditional syntax ("#ifdef", #if, #else, #elif, #define, etc.)
+  (`issue #837 <https://github.com/platformio/platformio/issues/837>`_)
 * Inject system environment variables to configuration settings in
   `Project Configuration File "platformio.ini" <http://docs.platformio.org/en/stable/projectconf.html>`__
   (`issue #792 <https://github.com/platformio/platformio/issues/792>`_)
@@ -31,8 +34,7 @@ PlatformIO 3.0
 * Improved handling of library dependencies specified in ``library.json`` manifest
   (`issue #814 <https://github.com/platformio/platformio/issues/814>`_)
 * Improved `Library Dependency Finder (LDF) <http://docs.platformio.org/en/stable/librarymanager/ldf.html>`__
-  for circular dependencies and fixed LDF C/C++ Preprocessor for conditional syntax
-  (`issue #837 <https://github.com/platformio/platformio/issues/837>`_)
+  for circular dependencies
 * Fixed issue with ``PATH`` auto-configuring for upload tools
 * Fixed ``99-platformio-udev.rules`` checker for Linux OS
 
diff --git a/platformio/builder/tools/piolib.py b/platformio/builder/tools/piolib.py
index f5f67708..c930696b 100644
--- a/platformio/builder/tools/piolib.py
+++ b/platformio/builder/tools/piolib.py
@@ -607,7 +607,8 @@ def BuildDependentLibraries(env, src_dir):
         # build full dependency graph
         found_lbs = [lb for lb in lib_builders if lb.dependent]
         for lb in lib_builders:
-            lb.search_deps_recursive(lib_builders, lb.get_src_files())
+            if lb in found_lbs:
+                lb.search_deps_recursive(lib_builders, lb.get_src_files())
         for lb in lib_builders:
             for deplb in lb.depbuilders[:]:
                 if deplb not in found_lbs:
diff --git a/platformio/builder/tools/platformio.py b/platformio/builder/tools/platformio.py
index 0a1d7e49..fa39934f 100644
--- a/platformio/builder/tools/platformio.py
+++ b/platformio/builder/tools/platformio.py
@@ -104,7 +104,7 @@ def BuildProgram(env):
     return program
 
 
-def ProcessFlags(env, flags):
+def ProcessFlags(env, flags):  # pylint: disable=too-many-branches
     if not flags:
         return
     if isinstance(flags, list):
diff --git a/platformio/managers/platform.py b/platformio/managers/platform.py
index 39319288..cc985ca7 100644
--- a/platformio/managers/platform.py
+++ b/platformio/managers/platform.py
@@ -477,7 +477,7 @@ class PlatformBase(PlatformPackagesMixin, PlatformRunMixin):
             }
         if "tool-scons" not in self.packages:
             self.packages['tool-scons'] = {
-                "version": "~3.20401.4",
+                "version": "~3.20501.1",
                 "optional": False
             }