diff --git a/mbed/mbed.py b/mbed/mbed.py
index 8354a44e..65d57900 100644
--- a/mbed/mbed.py
+++ b/mbed/mbed.py
@@ -1116,6 +1116,11 @@ def getlibs(self):
 
             for f in files:
                 if f.endswith('.lib') or f.endswith('.bld'):
+                    # If we are in a subdirectory that is importing mbed-os,
+                    # skip the import of mbed-os: the app will have already
+                    # imported mbed-os.
+                    if (f == 'mbed-os.lib') and (root != cwd_root):
+                        continue
                     repo = Repo.fromlib(os.path.join(root, f))
                     if repo:
                         yield repo