diff --git a/internal/erf/erf.go b/internal/erf/erf.go
index a160d8d..5e207fc 100644
--- a/internal/erf/erf.go
+++ b/internal/erf/erf.go
@@ -68,9 +68,18 @@ type resourceEntry struct {
 }
 
 // extensionTypes and typeExtensions must stay exact inverses of each other;
-// init() panics if they drift apart. Numbers below 0x0BB8 follow upstream
-// neverwinter.nim (neverwinter/restype.nim). The 0x0BB8 and up entries are
-// local additions for source formats upstream does not register.
+// init() panics if they drift apart.
+//
+// Numbers below 0x0BB8 follow upstream neverwinter.nim
+// (neverwinter/restype.nim). The 0x0BB8 and up entries are lyt/vis/mdx: real
+// Aurora archive types that NWN1 ships in its own data/*.bif but upstream
+// happens not to register. xoreos corroborates those three numbers
+// (src/aurora/types.h).
+//
+// This table is NWN:EE only. Do not add NWN2 formats (mdb, gr2, wlk, xml):
+// NWN:EE either gives that number to something else (2070 is xbc here and mdb
+// in NWN2) or has no number for it at all, so packing one into a HAK writes a
+// resource the game misreads. See the reserved list in erf_test.go.
 var extensionTypes = map[string]uint16{
 	"res": 0x0000,
 	"bmp": 0x0001,
@@ -131,9 +140,6 @@ var extensionTypes = map[string]uint16{
 	"lyt": 0x0BB8,
 	"vis": 0x0BB9,
 	"mdx": 0x0BC0,
-	"wlk": 0x0BCC,
-	"xml": 0x0BCD,
-	"gr2": 0x0FA3,
 }
 
 var typeExtensions = map[uint16]string{
@@ -196,9 +202,6 @@ var typeExtensions = map[uint16]string{
 	0x0BB8: "lyt",
 	0x0BB9: "vis",
 	0x0BC0: "mdx",
-	0x0BCC: "wlk",
-	0x0BCD: "xml",
-	0x0FA3: "gr2",
 }
 
 func init() {
diff --git a/internal/erf/erf_test.go b/internal/erf/erf_test.go
index 216d641..3634495 100644
--- a/internal/erf/erf_test.go
+++ b/internal/erf/erf_test.go
@@ -138,9 +138,6 @@ func TestExtensionMappingsSupportModernAssetTypes(t *testing.T) {
 		"lyt": 0x0BB8,
 		"vis": 0x0BB9,
 		"mdx": 0x0BC0,
-		"xml": 0x0BCD,
-		"wlk": 0x0BCC,
-		"gr2": 0x0FA3,
 	}
 	for ext, wantType := range cases {
 		gotType, ok := ResourceTypeForExtension(ext)
@@ -227,6 +224,19 @@ func TestRestypeTableMatchesUpstream(t *testing.T) {
 	}
 }
 
+// TestNWN2FormatsAreNotRegistered keeps NWN2 file formats out of an NWN:EE
+// table. mdb and gr2 have Aurora numbers that mean something else (or nothing)
+// in NWN:EE; wlk and xml have no archive number in any Aurora game, so the
+// values Crucible used for them were invented. Packing any of these into a HAK
+// writes a resource the game misreads.
+func TestNWN2FormatsAreNotRegistered(t *testing.T) {
+	for _, ext := range []string{"mdb", "gr2", "wlk", "xml"} {
+		if number, ok := ResourceTypeForExtension(ext); ok {
+			t.Errorf("%s is an NWN2 format but is registered as 0x%04X", ext, number)
+		}
+	}
+}
+
 // TestRestypeTablesAreMutualInverses is the check init() is meant to enforce.
 func TestRestypeTablesAreMutualInverses(t *testing.T) {
 	for ext, number := range extensionTypes {
diff --git a/internal/project/project.go b/internal/project/project.go
index 9334a2f..03954ed 100644
--- a/internal/project/project.go
+++ b/internal/project/project.go
@@ -31,7 +31,7 @@ var SourceExtensions = []string{
 }
 
 var AssetExtensions = []string{
-	".2da", ".bik", ".bmp", ".bmu", ".dds", ".dwk", ".gr2", ".itp", ".jpg", ".lod", ".lyt", ".mdl", ".mdx", ".mtr", ".plt", ".png", ".pwk", ".set", ".shd", ".tga", ".txi", ".uti", ".vis", ".wav", ".wlk", ".wok", ".xml",
+	".2da", ".bik", ".bmp", ".bmu", ".dds", ".dwk", ".itp", ".jpg", ".lod", ".lyt", ".mdl", ".mdx", ".mtr", ".plt", ".png", ".pwk", ".set", ".shd", ".tga", ".txi", ".uti", ".vis", ".wav", ".wok",
 }
 
 var BuiltinScriptPrefixes = []string{