diff --git a/main.lua b/main.lua
index 91dd937..8990e3e 100644
--- a/main.lua
+++ b/main.lua
@@ -424,12 +424,15 @@ local function get_topics_from_comparison_message(message)
     if comp then
         local topics = {}
         for topic in message:gmatch('[^'..comp..']+') do
-            topics[#topics+1]  =  clean_text(topic)
+            local topic_text   =  clean_text(topic)
+            if topic_text:match '[^%s]' then
+                topics[#topics+1]  =  topic_text
+            end
         end
         -- Rev
         if comp == '>' then  topics = reverse(topics)  end
         --
-        return topics
+        return (#topics >= 2) and topics or nil
     end
 
     -- Natural language comparisons