diff --git a/docs/rh-log.txt b/docs/rh-log.txt
index 0f7495f59..cc083c88a 100644
--- a/docs/rh-log.txt
+++ b/docs/rh-log.txt
@@ -1,4 +1,10 @@
-April 28, 2009  (Changes by Graf Zahl)
+April 29, 2009
+- Fixed: FWadCollection::CheckNumForName() read the lump each iteration before
+  checking for the end marker. On 32-bit systems, this is -1, but on 64-bit
+  systems, it is a very large integer that is highly unlikely to be in mapped
+  memory.
+
+April 28, 2009  (Changes by Graf Zahl)
 - Added ML_BLOCKUSE line flag, accessible through UDMF and Line_SetBlocking.
 
 April 25, 2009  (Changes by Graf Zahl)
diff --git a/lzma/C/CpuArch.h b/lzma/C/CpuArch.h
index 006361f2f..db441641b 100644
--- a/lzma/C/CpuArch.h
+++ b/lzma/C/CpuArch.h
@@ -47,6 +47,8 @@ about these properties of platform.
 
 #if defined(LITTLE_ENDIAN_UNALIGN) && defined(_WIN64) && (_MSC_VER >= 1300)
 
+unsigned long _byteswap_ulong(unsigned long);
+unsigned __int64 _byteswap_uint64(unsigned __int64);
 #pragma intrinsic(_byteswap_ulong)
 #pragma intrinsic(_byteswap_uint64)
 #define GetBe32(p) _byteswap_ulong(*(const UInt32 *)(const Byte *)(p))
diff --git a/src/w_wad.cpp b/src/w_wad.cpp
index a303310f7..73d45e9b7 100644
--- a/src/w_wad.cpp
+++ b/src/w_wad.cpp
@@ -418,6 +418,7 @@ int FWadCollection::CheckNumForName (const char *name, int space)
 
 int FWadCollection::CheckNumForName (const char *name, int space, int wadnum, bool exact)
 {
+	FResourceLump *lump;
 	char uname[8];
 	DWORD i;
 
@@ -428,18 +429,16 @@ int FWadCollection::CheckNumForName (const char *name, int space, int wadnum, bo
 
 	uppercopy (uname, name);
 	i = FirstLumpIndex[LumpNameHash (uname) % NumLumps];
-	FResourceLump *lump = LumpInfo[i].lump;
 
 	// If exact is true if will only find lumps in the same WAD, otherwise
 	// also those in earlier WADs.
 
 	while (i != NULL_INDEX &&
-		(*(QWORD *)&lump->Name != *(QWORD *)&uname ||
+		(lump = LumpInfo[i].lump, *(QWORD *)&lump->Name != *(QWORD *)&uname ||
 		lump->Namespace != space ||
 		 (exact? (LumpInfo[i].wadnum != wadnum) : (LumpInfo[i].wadnum > wadnum)) ))
 	{
 		i = NextLumpIndex[i];
-		lump = LumpInfo[i].lump;
 	}
 
 	return i != NULL_INDEX ? i : -1;