diff --git a/src/post_code.cpp b/src/post_code.cpp
index b1ffab8..82dba46 100644
--- a/src/post_code.cpp
+++ b/src/post_code.cpp
@@ -93,6 +93,10 @@
     }
 
     postCodes.insert(std::make_pair(tsUS, code));
+    if (postCodes.size() > MAX_POST_CODE_SIZE_PER_CYCLE)
+    {
+        postCodes.erase(postCodes.begin());
+    }
     serialize(fs::path(strPostCodeListPath));
 
 #ifdef ENABLE_BIOS_POST_CODE_LOG