diff --git a/NXDNControl.cpp b/NXDNControl.cpp
index 3526c9dde..1d253a08e 100644
--- a/NXDNControl.cpp
+++ b/NXDNControl.cpp
@@ -1059,7 +1059,7 @@ bool CNXDNControl::openFile()
 	if (m_fp == NULL)
 		return false;
 
-	::fwrite("NXDN", 1U, 3U, m_fp);
+	::fwrite("NXDN", 1U, 4U, m_fp);
 
 	return true;
 }