diff --git a/HISTORY.rst b/HISTORY.rst
index 95734b04..971990f0 100644
--- a/HISTORY.rst
+++ b/HISTORY.rst
@@ -12,7 +12,7 @@ PlatformIO 3.0
   - 100+ boards
   - Multiple architectures and development platforms
   - Zero Configuration
-  - Compatibility with the popular IDEs: Eclipse, Atom, VSCode, Sublime Text, etc
+  - Compatibility with the popular IDEs: Atom, VSCode, Eclipse, Sublime Text, etc
   - Windows, MacOS, Linux (+ARMv6-8)
 
 * Project generator for `VIM <http://docs.platformio.org/page/ide/vim.html>`__
@@ -21,6 +21,8 @@ PlatformIO 3.0
   (`issue #889 <https://github.com/platformio/platformio-core/issues/889>`_)
 * Handle dynamic ``SRC_FILTER`` environment variable from
   `library.json extra script <http://docs.platformio.org/page/librarymanager/config.html#extrascript>`__
+* Notify about multiple installations of PIO Core
+  (`issue #961 <https://github.com/platformio/platformio-core/issues/961>`_)
 * Improved auto-detecting of mbed-enabled media disks
 * Automatically update Git-submodules for development platforms and libraries
   that were installed from repository
diff --git a/docs b/docs
index 2c942c08..f49813d1 160000
--- a/docs
+++ b/docs
@@ -1 +1 @@
-Subproject commit 2c942c080b0159f8bc744a6441d68999538cfeec
+Subproject commit f49813d1105cb4624bd6ab4c965346adb714ad5d
diff --git a/platformio/maintenance.py b/platformio/maintenance.py
index 66d8eb75..a5c9c853 100644
--- a/platformio/maintenance.py
+++ b/platformio/maintenance.py
@@ -156,12 +156,29 @@ class Upgrader(object):
 
 
 def after_upgrade(ctx):
+    terminal_width, _ = click.get_terminal_size()
     last_version = app.get_state_item("last_version", "0.0.0")
     if last_version == __version__:
         return
 
     if last_version == "0.0.0":
         app.set_state_item("last_version", __version__)
+    elif semantic_version.Version.coerce(util.pepver_to_semver(
+            last_version)) > semantic_version.Version.coerce(
+                util.pepver_to_semver(__version__)):
+        click.secho("*" * terminal_width, fg="yellow")
+        click.secho(
+            "Obsolete PIO Core v%s is used (previous was %s)" %
+            (__version__, last_version),
+            fg="yellow")
+        click.secho(
+            "Please remove multiple PIO Cores from a system:", fg="yellow")
+        click.secho(
+            "http://docs.platformio.org/page/faq.html"
+            "#multiple-pio-cores-in-a-system",
+            fg="cyan")
+        click.secho("*" * terminal_width, fg="yellow")
+        return
     else:
         click.secho("Please wait while upgrading PlatformIO...", fg="yellow")
         app.clean_cache()
@@ -185,7 +202,6 @@ def after_upgrade(ctx):
         click.echo("")
 
     # PlatformIO banner
-    terminal_width, _ = click.get_terminal_size()
     click.echo("*" * terminal_width)
     click.echo("If you like %s, please:" % (click.style(
         "PlatformIO", fg="cyan")))