diff --git a/src/tools/wasm-shell.cpp b/src/tools/wasm-shell.cpp
index 2750f9d0b1e..c07108937c0 100644
--- a/src/tools/wasm-shell.cpp
+++ b/src/tools/wasm-shell.cpp
@@ -102,6 +102,7 @@ struct Shell {
     std::shared_ptr<Module> wasm;
     if (auto* quoted = std::get_if<QuotedModule>(&mod.module)) {
       wasm = std::make_shared<Module>();
+      wasm->features = FeatureSet::All;
       switch (quoted->type) {
         case QuotedModuleType::Text: {
           CHECK_ERR(parseModule(*wasm, quoted->module));
diff --git a/src/wasm/wasm-type.cpp b/src/wasm/wasm-type.cpp
index 3b0262ed2ee..129d4eef457 100644
--- a/src/wasm/wasm-type.cpp
+++ b/src/wasm/wasm-type.cpp
@@ -2419,6 +2419,12 @@ bool isValidSupertype(const HeapTypeInfo& sub, const HeapTypeInfo& super) {
     if (!super.described || sub.described->supertype != super.described) {
       return false;
     }
+  } else {
+    // A supertype of a type without a describes clause must also not have a
+    // describes clause.
+    if (super.described) {
+      return false;
+    }
   }
   SubTyper typer;
   switch (sub.kind) {