diff --git a/src/ir/possible-constant.h b/src/ir/possible-constant.h
index a75dd76299a..21422a3e880 100644
--- a/src/ir/possible-constant.h
+++ b/src/ir/possible-constant.h
@@ -120,8 +120,12 @@ struct PossibleConstantValues {
           value = val.and_(Literal(uint32_t(0xffff)));
         }
         break;
+      case Field::WaitQueue:
+        WASM_UNREACHABLE("not implemented");
+        break;
       case Field::not_packed:
         WASM_UNREACHABLE("unexpected packed type");
+        break;
     }
   }
 
diff --git a/src/parser/contexts.h b/src/parser/contexts.h
index 3978afff45d..c865272349b 100644
--- a/src/parser/contexts.h
+++ b/src/parser/contexts.h
@@ -149,6 +149,7 @@ struct NullTypeParserCtx {
 
   StorageT makeI8() { return Ok{}; }
   StorageT makeI16() { return Ok{}; }
+  StorageT makeWaitQueue() { return Ok{}; }
   StorageT makeStorageType(TypeT) { return Ok{}; }
 
   FieldT makeFieldType(StorageT, Mutability) { return Ok{}; }
@@ -308,6 +309,7 @@ template<typename Ctx> struct TypeParserCtx {
 
   StorageT makeI8() { return Field(Field::i8, Immutable); }
   StorageT makeI16() { return Field(Field::i16, Immutable); }
+  StorageT makeWaitQueue() { return Field(Field::WaitQueue, Immutable); }
   StorageT makeStorageType(TypeT type) { return Field(type, Immutable); }
 
   FieldT makeFieldType(FieldT field, Mutability mutability) {
diff --git a/src/parser/parsers.h b/src/parser/parsers.h
index d606563f1c1..2a3a5ec5a4e 100644
--- a/src/parser/parsers.h
+++ b/src/parser/parsers.h
@@ -717,6 +717,10 @@ template<typename Ctx> Result<typename Ctx::FieldT> storagetype(Ctx& ctx) {
   if (ctx.in.takeKeyword("i16"sv)) {
     return ctx.makeI16();
   }
+  if (ctx.in.takeKeyword("waitqueue"sv)) {
+    return ctx.makeWaitQueue();
+  }
+
   auto type = valtype(ctx);
   CHECK_ERR(type);
   return ctx.makeStorageType(*type);
diff --git a/src/wasm-binary.h b/src/wasm-binary.h
index 3bd3199b67a..fc37c0662a4 100644
--- a/src/wasm-binary.h
+++ b/src/wasm-binary.h
@@ -369,8 +369,9 @@ enum EncodedType {
   f64 = -0x4,  // 0x7c
   v128 = -0x5, // 0x7b
   // packed types
-  i8 = -0x8,  // 0x78
-  i16 = -0x9, // 0x77
+  i8 = -0x8,         // 0x78
+  i16 = -0x9,        // 0x77
+  waitQueue = -0x24, // 0x5c
   // reference types
   nullfuncref = -0xd,   // 0x73
   nullexternref = -0xe, // 0x72
diff --git a/src/wasm-interpreter.h b/src/wasm-interpreter.h
index 20578e03089..c2dff5ea34b 100644
--- a/src/wasm-interpreter.h
+++ b/src/wasm-interpreter.h
@@ -2752,6 +2752,10 @@ class ExpressionRunner : public OverriddenVisitor<SubType, Flow> {
         memcpy(&i, p, sizeof(i));
         return truncateForPacking(Literal(int32_t(i)), field);
       }
+      case Field::WaitQueue: {
+        WASM_UNREACHABLE("waitqueue not implemented");
+        break;
+      }
     }
     WASM_UNREACHABLE("unexpected type");
   }
diff --git a/src/wasm-type.h b/src/wasm-type.h
index 2364641a17c..ef892d92d41 100644
--- a/src/wasm-type.h
+++ b/src/wasm-type.h
@@ -701,6 +701,7 @@ struct Field {
     not_packed,
     i8,
     i16,
+    WaitQueue,
   } packedType; // applicable iff type=i32
   Mutability mutable_;
 
diff --git a/src/wasm/wasm-binary.cpp b/src/wasm/wasm-binary.cpp
index 85768b55fbc..633e6261278 100644
--- a/src/wasm/wasm-binary.cpp
+++ b/src/wasm/wasm-binary.cpp
@@ -1996,6 +1996,8 @@ void WasmBinaryWriter::writeField(const Field& field) {
       o << S32LEB(BinaryConsts::EncodedType::i8);
     } else if (field.packedType == Field::i16) {
       o << S32LEB(BinaryConsts::EncodedType::i16);
+    } else if (field.packedType == Field::WaitQueue) {
+      o << S32LEB(BinaryConsts::EncodedType::waitQueue);
     } else {
       WASM_UNREACHABLE("invalid packed type");
     }
@@ -2717,6 +2719,10 @@ void WasmBinaryReader::readTypes() {
       auto mutable_ = readMutability();
       return Field(Field::i16, mutable_);
     }
+    if (typeCode == BinaryConsts::EncodedType::waitQueue) {
+      auto mutable_ = readMutability();
+      return Field(Field::WaitQueue, mutable_);
+    }
     // It's a regular wasm value.
     auto type = makeType(typeCode);
     auto mutable_ = readMutability();
diff --git a/src/wasm/wasm-type.cpp b/src/wasm/wasm-type.cpp
index 83c58593010..a5f585a9277 100644
--- a/src/wasm/wasm-type.cpp
+++ b/src/wasm/wasm-type.cpp
@@ -1483,6 +1483,9 @@ unsigned Field::getByteSize() const {
       return 2;
     case Field::PackedType::not_packed:
       return 4;
+    case Field::PackedType::WaitQueue:
+      WASM_UNREACHABLE("waitqueue not implemented");
+      break;
   }
   WASM_UNREACHABLE("impossible packed type");
 }
@@ -1874,6 +1877,8 @@ std::ostream& TypePrinter::print(const Field& field) {
       os << "i8";
     } else if (packedType == Field::PackedType::i16) {
       os << "i16";
+    } else if (packedType == Field::PackedType::WaitQueue) {
+      os << "waitqueue";
     } else {
       WASM_UNREACHABLE("unexpected packed type");
     }
diff --git a/test/lit/waitqueue.wast b/test/lit/waitqueue.wast
new file mode 100644
index 00000000000..1a3e9726674
--- /dev/null
+++ b/test/lit/waitqueue.wast
@@ -0,0 +1,9 @@
+;; NOTE: Assertions have been generated by update_lit_checks.py and should not be edited.
+;; RUN: wasm-opt %s -all --roundtrip -S -o - | filecheck %s --check-prefix=RTRIP
+(module
+  ;; RTRIP:      (type $t (struct (field waitqueue)))
+  (type $t (struct (field waitqueue)))
+
+  ;; use $t so roundtripping doesn't drop the definition
+  (global (ref null $t) (ref.null $t))
+)