diff --git a/src/opendeepsearch/context_building/process_sources_pro.py b/src/opendeepsearch/context_building/process_sources_pro.py
index 91bb152..c52a9e0 100644
--- a/src/opendeepsearch/context_building/process_sources_pro.py
+++ b/src/opendeepsearch/context_building/process_sources_pro.py
@@ -71,7 +71,7 @@ async def _fetch_html_contents(self, links: List[str]) -> List[str]:
         return [x['no_extraction'].content for x in raw_contents.values()]
 
     def _process_html_content(self, html: str, query: str) -> str:
-        if not html:
+        if not html or not html.strip():
             return ""
         try:
             # Split the HTML content into chunks
@@ -100,4 +100,4 @@ def _update_sources_with_content(
         for (i, source), html in zip(valid_sources, html_contents):
             source['html'] = self._process_html_content(html, query)
             # sources[i] = source
-        return sources
\ No newline at end of file
+        return sources