diff --git a/nikola/utils.py b/nikola/utils.py
index 0067b34e4e..3dabb1222c 100644
--- a/nikola/utils.py
+++ b/nikola/utils.py
@@ -986,9 +986,12 @@ def get_asset_path(path, themes, files_folders={'files': ''}, _themes_dir='theme
     >>> print(get_asset_path('nikola.py', ['bootstrap3', 'base'], {'nikola': ''}))
     /.../nikola/nikola.py
 
-    >>> print(get_asset_path('nikola/nikola.py', ['bootstrap3', 'base'], {'nikola':'nikola'}))
+    >>> print(get_asset_path('nikola.py', ['bootstrap3', 'base'], {'nikola': 'nikola'}))
     None
 
+    >>> print(get_asset_path('nikola/nikola.py', ['bootstrap3', 'base'], {'nikola': 'nikola'}))
+    /.../nikola/nikola.py
+
     """
     for theme_name in themes:
         candidate = os.path.join(
@@ -998,9 +1001,11 @@ def get_asset_path(path, themes, files_folders={'files': ''}, _themes_dir='theme
         if os.path.isfile(candidate):
             return candidate
     for src, rel_dst in files_folders.items():
-        candidate = os.path.abspath(os.path.join(src, path))
-        if os.path.isfile(candidate):
-            return candidate
+        relpath = os.path.relpath(path, rel_dst)
+        if not relpath.startswith('..' + os.path.sep):
+            candidate = os.path.abspath(os.path.join(src, relpath))
+            if os.path.isfile(candidate):
+                return candidate
 
     if output_dir:
         candidate = os.path.join(output_dir, path)