diff --git a/src/summary.rs b/src/summary.rs
index c13746b..da8f50f 100644
--- a/src/summary.rs
+++ b/src/summary.rs
@@ -2019,11 +2019,13 @@ class {camel}(Protocol):
                     | TypeDefKind::Result(_)
                     | TypeDefKind::Handle(_) => (None, Vec::new()),
                     TypeDefKind::Stream(ty) => {
-                        let canonical = canonical_payload(self.resolve, &mut types, ty);
-                        let code = if stream_payloads.contains(&canonical) {
+                        let snake = ty
+                            .map(|ty| names.mangle_name(ty))
+                            .unwrap_or_else(|| "unit".into());
+                        let code = if stream_payloads.contains(&snake) {
                             None
                         } else {
-                            stream_payloads.insert(canonical);
+                            stream_payloads.insert(snake.clone());
 
                             Some(if let Some(Type::U8 | Type::S8) = ty {
                                 if stub_runtime_calls {
@@ -2044,9 +2046,6 @@ def byte_stream() -> tuple[ByteStreamWriter, ByteStreamReader]:
                                     )
                                 }
                             } else {
-                                let snake = ty
-                                    .map(|ty| names.mangle_name(ty))
-                                    .unwrap_or_else(|| "unit".into());
                                 let camel = ty
                                     .map(|ty| names.type_name(ty, &seen, None))
                                     .unwrap_or_else(|| "None".into());
@@ -2073,15 +2072,14 @@ def {snake}_stream() -> tuple[StreamWriter[{camel}], StreamReader[{camel}]]:
                         (code.map(Code::Shared), Vec::new())
                     }
                     TypeDefKind::Future(ty) => {
-                        let canonical = canonical_payload(self.resolve, &mut types, ty);
-                        let code = if future_payloads.contains(&canonical) {
+                        let snake = ty
+                            .map(|ty| names.mangle_name(ty))
+                            .unwrap_or_else(|| "unit".into());
+                        let code = if future_payloads.contains(&snake) {
                             None
                         } else {
-                            future_payloads.insert(canonical);
+                            future_payloads.insert(snake.clone());
 
-                            let snake = ty
-                                .map(|ty| names.mangle_name(ty))
-                                .unwrap_or_else(|| "unit".into());
                             let camel = ty
                                 .map(|ty| names.type_name(ty, &seen, None))
                                 .unwrap_or_else(|| "None".into());
@@ -3260,19 +3258,6 @@ fn docstring(docs: Option<&str>, indent_level: usize, error: Option<&str>) -> St
     }
 }
 
-fn canonical_payload(resolve: &Resolve, types: &mut Types, ty: &Option<Type>) -> Option<Type> {
-    match ty {
-        Some(Type::Id(id)) => {
-            let id = types.get_representative_type(*id);
-            match resolve.types[id].kind {
-                TypeDefKind::Type(t) => Some(t),
-                _ => Some(Type::Id(id)),
-            }
-        }
-        other => *other,
-    }
-}
-
 fn dealias(resolve: &Resolve, mut id: TypeId) -> TypeId {
     loop {
         match &resolve.types[id].kind {
diff --git a/src/test/python_source/app.py b/src/test/python_source/app.py
index 1785503..6d4a74f 100644
--- a/src/test/python_source/app.py
+++ b/src/test/python_source/app.py
@@ -19,6 +19,7 @@
 from tests.imports.componentize_py.test import host_thing_interface
 from tests.exports.componentize_py.test import resource_alias2
 from tests.exports.componentize_py.test import streams_and_futures
+from tests.exports.componentize_py.test import similar_streams_and_futures
 from typing import Tuple, List, Optional
 from foo_sdk.wit.exports.foo import sdk as foo_exports
 from foo_sdk.wit.exports.foo.sdk import foo_interface as foo_iface
@@ -297,3 +298,11 @@ def test(self, s: str) -> str:
 class BarInterface(bar_exports.BarInterface):
     def test(self, s: str) -> str:
         return bar_test(f"{s} BarInterface.test")
+
+@exports.similar_streams_and_futures.guest
+class SimilarStreamsAndFutures(exports.SimilarStreamsAndFutures):
+    async def baz(self) -> tuple[StreamReader[similar_streams_and_futures.Foo], StreamReader[similar_streams_and_futures.Bar], FutureReader[similar_streams_and_futures.Foo], FutureReader[similar_streams_and_futures.Bar]]:
+        return (tests.componentize_py_test_similar_streams_and_futures_foo_stream()[1],
+                tests.componentize_py_test_similar_streams_and_futures_bar_stream()[1],
+                tests.componentize_py_test_similar_streams_and_futures_foo_future(lambda: similar_streams_and_futures.Foo_A())[1],
+                tests.componentize_py_test_similar_streams_and_futures_bar_future(lambda: similar_streams_and_futures.Bar_A())[1])
diff --git a/src/test/tests.rs b/src/test/tests.rs
index 0392abc..fe90903 100644
--- a/src/test/tests.rs
+++ b/src/test/tests.rs
@@ -1400,6 +1400,33 @@ fn test_echo_stream_u8(delay: bool) -> Result<()> {
     })
 }
 
+#[test]
+fn test_similar_streams_and_futures() -> Result<()> {
+    // Previously, `componentize-py` would coalesce stream and future
+    // constructor functions whose payloads were structurally (but not
+    // nominally) equivalent, making the names unpredictable.  This test ensures
+    // we don't do that anymore.
+    TESTER.test(|world, store, runtime| {
+        runtime.block_on(async {
+            store
+                .run_concurrent(async |store| {
+                    // Just call the function and make sure the stream and
+                    // future constructor functions are resolved in the Python
+                    // code:
+                    world
+                        .componentize_py_test_similar_streams_and_futures()
+                        .call_baz(store)
+                        .await?;
+
+                    anyhow::Ok(())
+                })
+                .await?
+        })?;
+
+        Ok(())
+    })
+}
+
 struct OptionProducer<T> {
     source: Option<T>,
     sleep: Pin<Box<dyn Future<Output = ()> + Send>>,
diff --git a/src/test/wit/tests.wit b/src/test/wit/tests.wit
index afce618..72ccabb 100644
--- a/src/test/wit/tests.wit
+++ b/src/test/wit/tests.wit
@@ -165,6 +165,18 @@ interface streams-and-futures {
   dropped-future-reader-host: async func(value: string) -> tuple<future<host-thing>, future<host-thing>>;
 }
 
+interface similar-streams-and-futures {
+  variant foo {
+    a, b, c
+  }
+
+  variant bar {
+    a, b, c
+  }
+
+  baz: async func() -> tuple<stream<foo>, stream<bar>, future<foo>, future<bar>>;
+}
+
 world tests {
   use resource-alias1.{thing};
   use resource-floats.{float};
@@ -190,6 +202,7 @@ world tests {
   import resource-borrow-in-record;
   export resource-borrow-in-record;
   export streams-and-futures;
+  export similar-streams-and-futures;
 
   export resource-floats-exports: interface {
     resource float {