diff --git a/src/d_iwad.cpp b/src/d_iwad.cpp
index 3fc365e8c..a8d60e1ce 100644
--- a/src/d_iwad.cpp
+++ b/src/d_iwad.cpp
@@ -435,6 +435,11 @@ int FIWadManager::IdentifyVersion (TArray<FString> &wadfiles, const char *iwad,
 				}
 			}
 		}
+		TArray<FString> gog_paths = I_GetGogPaths();
+		for (i = 0; i < gog_paths.Size(); ++i)
+		{
+			CheckIWAD (gog_paths[i], &wads[0]);
+		}
 		TArray<FString> steam_path = I_GetSteamPath();
 		for (i = 0; i < steam_path.Size(); ++i)
 		{
diff --git a/src/posix/i_system.cpp b/src/posix/i_system.cpp
index fd6bb4c0c..84b953717 100644
--- a/src/posix/i_system.cpp
+++ b/src/posix/i_system.cpp
@@ -758,3 +758,9 @@ unsigned int I_MakeRNGSeed()
 	}
 	return seed;
 }
+
+TArray<FString> I_GetGogPaths()
+{
+    // GOG's Doom games are Windows only at the moment
+    return TArray<FString>();
+}
diff --git a/src/posix/i_system.h b/src/posix/i_system.h
index abda490c4..391503602 100644
--- a/src/posix/i_system.h
+++ b/src/posix/i_system.h
@@ -124,6 +124,8 @@ int I_PickIWad (WadStuff *wads, int numwads, bool queryiwad, int defaultiwad);
 // directories for IWADs if the user purchased any through Steam.
 TArray<FString> I_GetSteamPath();
 
+TArray<FString> I_GetGogPaths();
+
 // The ini could not be saved at exit
 bool I_WriteIniFailed ();
 
diff --git a/src/win32/i_system.cpp b/src/win32/i_system.cpp
index 6d8fb8595..372da8685 100644
--- a/src/win32/i_system.cpp
+++ b/src/win32/i_system.cpp
@@ -1504,30 +1504,83 @@ int I_FindClose(void *handle)
 
 static bool QueryPathKey(HKEY key, const char *keypath, const char *valname, FString &value)
 {
-	HKEY steamkey;
+	HKEY pathkey;
 	DWORD pathtype;
 	DWORD pathlen;
 	LONG res;
 
-	if(ERROR_SUCCESS == RegOpenKeyEx(key, keypath, 0, KEY_QUERY_VALUE, &steamkey))
+	if(ERROR_SUCCESS == RegOpenKeyEx(key, keypath, 0, KEY_QUERY_VALUE, &pathkey))
 	{
-		if (ERROR_SUCCESS == RegQueryValueEx(steamkey, valname, 0, &pathtype, NULL, &pathlen) &&
+		if (ERROR_SUCCESS == RegQueryValueEx(pathkey, valname, 0, &pathtype, NULL, &pathlen) &&
 			pathtype == REG_SZ && pathlen != 0)
 		{
 			// Don't include terminating null in count
 			char *chars = value.LockNewBuffer(pathlen - 1);
-			res = RegQueryValueEx(steamkey, valname, 0, NULL, (LPBYTE)chars, &pathlen);
+			res = RegQueryValueEx(pathkey, valname, 0, NULL, (LPBYTE)chars, &pathlen);
 			value.UnlockBuffer();
 			if (res != ERROR_SUCCESS)
 			{
 				value = "";
 			}
 		}
-		RegCloseKey(steamkey);
+		RegCloseKey(pathkey);
 	}
 	return value.IsNotEmpty();
 }
 
+//==========================================================================
+//
+// I_GetGogPaths
+//
+// Check the registry for GOG installation paths, so we can search for IWADs
+// that were bought from GOG.com. This is a bit different from the Steam
+// version because each game has its own independent installation path, no
+// such thing as <steamdir>/SteamApps/common/<GameName>.
+//
+//==========================================================================
+
+TArray<FString> I_GetGogPaths()
+{
+	TArray<FString> result;
+	FString path;
+	FString gamepath;
+
+#ifdef _WIN64
+	FString gogregistrypath = "Software\\Wow6432Node\\GOG.com\\Games";
+#else
+	// If a 32-bit ZDoom runs on a 64-bit Windows, this will be transparently and
+	// automatically redirected to the Wow6432Node address instead, so this address
+	// should be safe to use in all cases.
+	FString gogregistrypath = "Software\\GOG.com\\Games";
+#endif
+
+	// Look for Ultimate Doom
+	gamepath = gogregistrypath + "\\1435827232";
+	if (QueryPathKey(HKEY_LOCAL_MACHINE, gamepath.GetChars(), "Path", path))
+	{
+		result.Push(path);	// directly in install folder
+	}
+
+	// Look for Doom II
+	gamepath = gogregistrypath + "\\1435848814";
+	if (QueryPathKey(HKEY_LOCAL_MACHINE, gamepath.GetChars(), "Path", path))
+	{
+		result.Push(path + "/doom2");	// in a subdirectory
+		// If direct support for the Master Levels is ever added, they are in path + /master/wads
+	}
+
+	// Look for Final Doom
+	gamepath = gogregistrypath + "\\1435848742";
+	if (QueryPathKey(HKEY_LOCAL_MACHINE, gamepath.GetChars(), "Path", path))
+	{
+		// in subdirectories
+		result.Push(path + "/TNT");
+		result.Push(path + "/Plutonia");
+	}
+
+	return result;
+}
+
 //==========================================================================
 //
 // I_GetSteamPath
diff --git a/src/win32/i_system.h b/src/win32/i_system.h
index 566ca1977..03f4f3c0f 100644
--- a/src/win32/i_system.h
+++ b/src/win32/i_system.h
@@ -168,6 +168,9 @@ void I_SetWndProc();
 // directories for IWADs if the user purchased any through Steam.
 TArray<FString> I_GetSteamPath();
 
+// [GZ] Same deal for GOG paths
+TArray<FString> I_GetGogPaths();
+
 // Damn Microsoft for doing Get/SetWindowLongPtr half-assed. Instead of
 // giving them proper prototypes under Win32, they are just macros for
 // Get/SetWindowLong, meaning they take LONGs and not LONG_PTRs.
diff --git a/wadsrc/static/actors/doom/spidermaster.txt b/wadsrc/static/actors/doom/spidermaster.txt
index 97ebbf143..c2a742f1e 100644
--- a/wadsrc/static/actors/doom/spidermaster.txt
+++ b/wadsrc/static/actors/doom/spidermaster.txt
@@ -6,7 +6,7 @@
 ACTOR SpiderMastermind
 {
 	Health 3000
-	Radius 100
+	Radius 128
 	Height 100
 	Mass 1000
 	Speed 12