diff --git a/cmd/conformance/core.lua b/cmd/conformance/core.lua
index 5095222b45b6462e1455b25a63f88cbff9d919da..217b4f38310716e948f9b97ea7428f52facc9f11 100644
--- a/cmd/conformance/core.lua
+++ b/cmd/conformance/core.lua
@@ -24,6 +24,11 @@     ['conformance.FailureSet'] =
         conformance.FailureSet_descriptor,
 }
 
+-- Register the test message in the runtime's WKT registry so Any fields
+-- with `@type` pointing at a non-WKT user type (the conformance suite uses
+-- TestAllTypesProto3 itself inside some Any tests) resolve in JSON decode.
+pb.register(proto3_tests.TestAllTypesProto3_descriptor)
+
 local WIRE_FORMAT = conformance.WireFormat
 local PROTOBUF    = WIRE_FORMAT.PROTOBUF
 local JSON        = WIRE_FORMAT.JSON
diff --git a/runtime/pb/wkt.lua b/runtime/pb/wkt.lua
index 531d9db166b4f0b574028b1fa478dccf715aa795..690fbc07f18b6df9b3fcca7d46f7c3e8935aae3f 100644
--- a/runtime/pb/wkt.lua
+++ b/runtime/pb/wkt.lua
@@ -563,4 +563,14 @@ M.FieldMask_encode     = fieldmask_encode
 M.FieldMask_decode     = fieldmask_decode
 M.FieldMask_descriptor = {name='google.protobuf.FieldMask', encode=fieldmask_encode, decode=fieldmask_decode}
 
+-- Self-register every WKT so `pb.lookup(type_url)` resolves them without
+-- the user having to call `pb.register` explicitly. This is what makes
+-- Any-of-WKT JSON decode work out of the box.
+for k, v in pairs(M) do
+    if type(k) == 'string' and k:sub(-11) == '_descriptor'
+       and type(v) == 'table' and v.name ~= nil then
+        M.register(v)
+    end
+end
+
 return M
diff --git a/test/conformance/known_failures.txt b/test/conformance/known_failures.txt
index e15f5793a5132a4e5a82340d6394ec32a927c14a..288c8fc1a3e49a6f6e7582977c260e9af71232da 100644
--- a/test/conformance/known_failures.txt
+++ b/test/conformance/known_failures.txt
@@ -33,21 +33,11 @@ Recommended.Proto3.ProtobufInput.RejectInvalidUtf8.String.Singular
 Recommended.Proto3.ProtobufInput.ValidDataOneofBinary.MESSAGE.Merge.ProtobufOutput
 Required.Proto3.JsonInput.AllFieldAcceptNull.JsonOutput
 Required.Proto3.JsonInput.AllFieldAcceptNull.ProtobufOutput
-Required.Proto3.JsonInput.Any.ProtobufOutput
 Required.Proto3.JsonInput.AnyNested.JsonOutput
-Required.Proto3.JsonInput.AnyNested.ProtobufOutput
-Required.Proto3.JsonInput.AnyUnorderedTypeTag.ProtobufOutput
-Required.Proto3.JsonInput.AnyWithDuration.ProtobufOutput
-Required.Proto3.JsonInput.AnyWithFieldMask.ProtobufOutput
 Required.Proto3.JsonInput.AnyWithInt32ValueWrapper.JsonOutput
-Required.Proto3.JsonInput.AnyWithInt32ValueWrapper.ProtobufOutput
 Required.Proto3.JsonInput.AnyWithStruct.JsonOutput
-Required.Proto3.JsonInput.AnyWithStruct.ProtobufOutput
-Required.Proto3.JsonInput.AnyWithTimestamp.ProtobufOutput
 Required.Proto3.JsonInput.AnyWithValueForInteger.JsonOutput
-Required.Proto3.JsonInput.AnyWithValueForInteger.ProtobufOutput
 Required.Proto3.JsonInput.AnyWithValueForJsonObject.JsonOutput
-Required.Proto3.JsonInput.AnyWithValueForJsonObject.ProtobufOutput
 Required.Proto3.JsonInput.FieldNameInSnakeCase.ProtobufOutput
 Required.Proto3.JsonInput.Int64FieldMaxValueNotQuoted.JsonOutput
 Required.Proto3.JsonInput.Int64FieldMaxValueNotQuoted.ProtobufOutput