diff --git a/docs/user-guide/configuration.md b/docs/user-guide/configuration.md
index 76652fe0..40f45196 100644
--- a/docs/user-guide/configuration.md
+++ b/docs/user-guide/configuration.md
@@ -181,8 +181,8 @@ up.
 
 Lets you set the directory containing the documentation source markdown files.
 This can either be a relative directory, in which case it is resolved relative
-to the directory containing you configuration file, or it can be an absolute
-directory path.
+to the directory containing your configuration file, or it can be an absolute
+directory path from the root of your local file system.
 
 **default**: `'docs'`
 
@@ -190,8 +190,8 @@ directory path.
 
 Lets you set the directory where the output HTML and other files are created.
 This can either be a relative directory, in which case it is resolved relative
-to the directory containing you configuration file, or it can be an absolute
-directory path.
+to the directory containing your configuration file, or it can be an absolute
+directory path from the root of your local file system.
 
 **default**: `'site'`
 
diff --git a/mkdocs/config/config_options.py b/mkdocs/config/config_options.py
index 7fa3ac6f..d5e656fd 100644
--- a/mkdocs/config/config_options.py
+++ b/mkdocs/config/config_options.py
@@ -253,14 +253,14 @@ class SiteDir(Dir):
         # Validate that the docs_dir and site_dir don't contain the
         # other as this will lead to copying back and forth on each
         # and eventually make a deep nested mess.
-        if (config['docs_dir'] + os.sep).startswith(config['site_dir'] + os.sep):
+        if (config['docs_dir'] + os.sep).startswith(config['site_dir'].rstrip(os.sep) + os.sep):
             raise ValidationError(
                 ("The 'docs_dir' should not be within the 'site_dir' as this "
                  "can mean the source files are overwritten by the output or "
                  "it will be deleted if --clean is passed to mkdocs build."
                  "(site_dir: '{0}', docs_dir: '{1}')"
                  ).format(config['site_dir'], config['docs_dir']))
-        elif (config['site_dir'] + os.sep).startswith(config['docs_dir'] + os.sep):
+        elif (config['site_dir'] + os.sep).startswith(config['docs_dir'].rstrip(os.sep) + os.sep):
             raise ValidationError(
                 ("The 'site_dir' should not be within the 'docs_dir' as this "
                  "leads to the build directory being copied into itself and "
diff --git a/mkdocs/tests/config/config_options_tests.py b/mkdocs/tests/config/config_options_tests.py
index b4f12734..041dd21b 100644
--- a/mkdocs/tests/config/config_options_tests.py
+++ b/mkdocs/tests/config/config_options_tests.py
@@ -228,6 +228,7 @@ class SiteDirTest(unittest.TestCase):
             {'docs_dir': 'docs', 'site_dir': ''},
             {'docs_dir': '', 'site_dir': ''},
             {'docs_dir': j('..', parent_dir, 'docs'), 'site_dir': 'docs'},
+            {'docs_dir': 'docs', 'site_dir': '/'}
         )
 
         for test_config in test_configs:
@@ -242,6 +243,7 @@ class SiteDirTest(unittest.TestCase):
             {'docs_dir': 'docs', 'site_dir': j('docs', 'site')},
             {'docs_dir': '.', 'site_dir': 'site'},
             {'docs_dir': '', 'site_dir': 'site'},
+            {'docs_dir': '/', 'site_dir': 'site'},
         )
 
         for test_config in test_configs: