diff --git a/src/gpodder/gtkui/interface/addpodcast.py b/src/gpodder/gtkui/interface/addpodcast.py
index a094a80a9..97bef3f98 100644
--- a/src/gpodder/gtkui/interface/addpodcast.py
+++ b/src/gpodder/gtkui/interface/addpodcast.py
@@ -49,9 +49,10 @@ def new(self):
             clipboard = Gtk.Clipboard.get(Gdk.SELECTION_CLIPBOARD)
 
             def receive_clipboard_text(clipboard, text, second_try):
-                # Heuristic: If there is a space in the clipboard
-                # text, assume it's some arbitrary text, and no URL
-                if text is not None and ' ' not in text:
+                # Heuristic: If space is present in clipboard text
+                # normalize_feed_url will either fix to valid url or
+                # return None if URL cannot be validated
+                if text is not None:
                     url = util.normalize_feed_url(text)
                     if url is not None:
                         self.entry_url.set_text(url)
@@ -72,7 +73,7 @@ def on_btn_paste_clicked(self, widget):
 
     def receive_clipboard_text(self, clipboard, text, data=None):
         if text is not None:
-            self.entry_url.set_text(text)
+            self.entry_url.set_text(text).strip()
         else:
             self.show_message(_('Nothing to paste.'), _('Clipboard is empty'))
 
diff --git a/src/gpodder/util.py b/src/gpodder/util.py
index 9523e45d8..edc48b757 100644
--- a/src/gpodder/util.py
+++ b/src/gpodder/util.py
@@ -73,14 +73,14 @@
 try:
     import html5lib
 except ImportError:
-    logger.warn('html5lib not found, falling back to HTMLParser')
+    logger.warning("html5lib was not found, fall-back to HTMLParser")
     html5lib = None
 
 if gpodder.ui.win32:
     try:
         import gpodder.utilwin32ctypes as win32file
     except ImportError:
-        logger.warn('Running on Win32 but utilwin32ctypes can\'t be loaded.')
+        logger.warning('Running on Win32: utilwin32ctypes cannot be loaded')
         win32file = None
 
 _ = gpodder.gettext
@@ -248,6 +248,12 @@ def normalize_feed_url(url):
     if not url or len(url) < 8:
         return None
 
+    # Removes leading and/or trailing whitespaces - if url contains whitespaces
+    # in between after str.strip() -> conclude invalid url & return None
+    url = url.strip()
+    if ' ' in url:
+        return None
+
     # This is a list of prefixes that you can use to minimize the amount of
     # keystrokes that you have to use.
     # Feel free to suggest other useful prefixes, and I'll add them here.