diff --git a/oml/media/epub.py b/oml/media/epub.py
index b848200..81ccb17 100644
--- a/oml/media/epub.py
+++ b/oml/media/epub.py
@@ -178,6 +178,9 @@ def info(epub):
         data['date'] = data['date'].split('T')[0]
     if 'language' in data and isinstance(data['language'], str):
         data['language'] = get_language(data['language'])
+    for key in list(data):
+        if isinstance(data[key], str) and not data[key].strip():
+            del data[key]
     return data
 
 def extract_text(path):
diff --git a/oml/media/pdf.py b/oml/media/pdf.py
index eb7502c..fdf5a01 100644
--- a/oml/media/pdf.py
+++ b/oml/media/pdf.py
@@ -224,6 +224,9 @@ def info(pdf):
         for key in ('title', 'author', 'producer', 'creator'):
             if key in data:
                 del data[key]
+    for key in list(data):
+        if isinstance(data[key], str) and not data[key].strip():
+            del data[key]
     return data
 
 '''