Index: source/ps/XML/Xeromyces.cpp
===================================================================
--- source/ps/XML/Xeromyces.cpp
+++ source/ps/XML/Xeromyces.cpp
@@ -1,4 +1,4 @@
-/* Copyright (C) 2015 Wildfire Games.
+/* Copyright (C) 2018 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -173,10 +173,12 @@
 		return PSRETURN_Xeromyces_XMLParseError;
 	}
 
+	bool valid = true;
 	{
 		CScopeLock lock(g_ValidatorCacheLock);
 		RelaxNGValidator& validator = GetValidator(validatorName);
-		if (validator.CanValidate() && !validator.ValidateEncoded(doc))
+		valid = !validator.CanValidate() || validator.ValidateEncoded(doc);
+		if (!valid)
 			// For now, log the error and continue, in the future we might fail
 			LOGERROR("CXeromyces: failed to validate XML file %s", filename.string8());
 	}
@@ -186,8 +188,10 @@
 
 	xmlFreeDoc(doc);
 
-	// Save the file to disk, so it can be loaded quickly next time
-	vfs->CreateFile(xmbPath, writeBuffer.Data(), writeBuffer.Size());
+	// Save the file to disk, so it can be loaded quickly next time.
+	// Don't save if invalid, because we want the syntax error every program start.
+	if (valid)
+		vfs->CreateFile(xmbPath, writeBuffer.Data(), writeBuffer.Size());
 
 	m_XMBBuffer = writeBuffer.Data(); // add a reference