diff --git a/src/calibre/gui2/open_with.py b/src/calibre/gui2/open_with.py
index ac5e0b2b02..674d59527f 100644
--- a/src/calibre/gui2/open_with.py
+++ b/src/calibre/gui2/open_with.py
@@ -17,7 +17,7 @@ from PyQt5.Qt import (
 
 from calibre import as_unicode
 from calibre.constants import iswindows, isosx
-from calibre.gui2 import error_dialog, choose_files, choose_images, elided_text, sanitize_env_vars, Application
+from calibre.gui2 import error_dialog, choose_files, choose_images, elided_text, sanitize_env_vars, Application, choose_osx_app
 from calibre.gui2.widgets2 import Dialog
 from calibre.gui2.progress_indicator import ProgressIndicator
 from calibre.utils.config import JSONConfig
@@ -125,7 +125,7 @@ if iswindows:
 elif isosx:
     # OS X {{{
     oprefs = JSONConfig('osx_open_with')
-    from calibre.utils.open_with.osx import find_programs, get_icon, entry_to_cmdline
+    from calibre.utils.open_with.osx import find_programs, get_icon, entry_to_cmdline, get_bundle_data
 
     def entry_sort_key(entry):
         return sort_key(entry.get('name') or '')
@@ -148,7 +148,21 @@ elif isosx:
         ans.setToolTip(_('Application path:') + '\n' + entry['path'])
 
     def choose_manually(filetype, parent):
-        raise NotImplementedError()
+        ans = choose_osx_app(parent, 'choose-open-with-program-manually', _('Choose a program to open %s files') % filetype.upper())
+        if ans:
+            ans = ans[0]
+            if os.path.isdir(ans):
+                app = get_bundle_data(ans)
+                if app is None:
+                    return error_dialog(parent, _('Invalid Application'), _(
+                        '%s is not a valid OS X application bundle.') % ans, show=True)
+                return app
+            if not os.access(ans, os.X_OK):
+                return error_dialog(parent, _('Cannot execute'), _(
+                    'The program %s is not an executable file') % ans, show=True)
+
+            return {'path':ans, 'name': os.path.basename(ans)}
+
     # }}}
 
 else:
diff --git a/src/calibre/utils/open_with/osx.py b/src/calibre/utils/open_with/osx.py
index cd8735aa17..d62460d648 100644
--- a/src/calibre/utils/open_with/osx.py
+++ b/src/calibre/utils/open_with/osx.py
@@ -331,6 +331,8 @@ def get_icon(path, pixmap_to_data=None, as_data=False, size=64):
 
 def entry_to_cmdline(entry, path):
     app = entry['path']
-    if not os.path.isdir(app) and 'identifier' in entry:
+    if os.path.isdir(app):
+        return ['open', '-a', app, path]
+    if 'identifier' in entry:
         return ['open', '-b', entry['identifier'], path]
-    return ['open', '-a', app, path]
+    return [app, path]