diff --git a/3rdParty/StormLib/src/SFileOpenArchive.cpp b/3rdParty/StormLib/src/SFileOpenArchive.cpp
index 381300bc7..ea88216fc 100644
--- a/3rdParty/StormLib/src/SFileOpenArchive.cpp
+++ b/3rdParty/StormLib/src/SFileOpenArchive.cpp
@@ -164,7 +164,8 @@ bool WINAPI SFileSetArchiveMarkers(PSFILE_MARKERS pMarkers)
     InitializeMpqCryptography();
 
     // Remember the marker for MPQ header
-    g_dwMpqSignature = pMarkers->dwSignature;
+    if(pMarkers->dwSignature != 0)
+        g_dwMpqSignature = pMarkers->dwSignature;
 
     // Remember the encryption key for hash table
     if(pMarkers->szHashTableKey != NULL)