diff --git a/library/proc_macro/src/bridge/client.rs b/library/proc_macro/src/bridge/client.rs
index 421dd30273f..068f3e241be 100644
--- a/library/proc_macro/src/bridge/client.rs
+++ b/library/proc_macro/src/bridge/client.rs
@@ -427,11 +427,7 @@ impl Client<crate::TokenStream, crate::TokenStream> {
         Client {
             get_handle_counters: HandleCounters::get,
             run: super::selfless_reify::reify_to_extern_c_fn_hrt_bridge(move |bridge| {
-                run_client(bridge, |input| {
-                    f(crate::TokenStream(Some(input)))
-                        .0
-                        .unwrap_or_else(|| TokenStream::concat_streams(None, vec![]))
-                })
+                run_client(bridge, |input| f(crate::TokenStream(Some(input))).0)
             }),
             _marker: PhantomData,
         }
@@ -446,9 +442,7 @@ impl Client<(crate::TokenStream, crate::TokenStream), crate::TokenStream> {
             get_handle_counters: HandleCounters::get,
             run: super::selfless_reify::reify_to_extern_c_fn_hrt_bridge(move |bridge| {
                 run_client(bridge, |(input, input2)| {
-                    f(crate::TokenStream(Some(input)), crate::TokenStream(Some(input2)))
-                        .0
-                        .unwrap_or_else(|| TokenStream::concat_streams(None, vec![]))
+                    f(crate::TokenStream(Some(input)), crate::TokenStream(Some(input2))).0
                 })
             }),
             _marker: PhantomData,
diff --git a/library/proc_macro/src/bridge/server.rs b/library/proc_macro/src/bridge/server.rs
index d98def36a3c..3672299f18f 100644
--- a/library/proc_macro/src/bridge/server.rs
+++ b/library/proc_macro/src/bridge/server.rs
@@ -273,13 +273,17 @@ fn run_server<
 }
 
 impl client::Client<crate::TokenStream, crate::TokenStream> {
-    pub fn run<S: Server>(
+    pub fn run<S>(
         &self,
         strategy: &impl ExecutionStrategy,
         server: S,
         input: S::TokenStream,
         force_show_panics: bool,
-    ) -> Result<S::TokenStream, PanicMessage> {
+    ) -> Result<S::TokenStream, PanicMessage>
+    where
+        S: Server,
+        S::TokenStream: Default,
+    {
         let client::Client { get_handle_counters, run, _marker } = *self;
         run_server(
             strategy,
@@ -289,19 +293,23 @@ impl client::Client<crate::TokenStream, crate::TokenStream> {
             run,
             force_show_panics,
         )
-        .map(<MarkedTypes<S> as Types>::TokenStream::unmark)
+        .map(|s| <Option<<MarkedTypes<S> as Types>::TokenStream>>::unmark(s).unwrap_or_default())
     }
 }
 
 impl client::Client<(crate::TokenStream, crate::TokenStream), crate::TokenStream> {
-    pub fn run<S: Server>(
+    pub fn run<S>(
         &self,
         strategy: &impl ExecutionStrategy,
         server: S,
         input: S::TokenStream,
         input2: S::TokenStream,
         force_show_panics: bool,
-    ) -> Result<S::TokenStream, PanicMessage> {
+    ) -> Result<S::TokenStream, PanicMessage>
+    where
+        S: Server,
+        S::TokenStream: Default,
+    {
         let client::Client { get_handle_counters, run, _marker } = *self;
         run_server(
             strategy,
@@ -314,6 +322,6 @@ impl client::Client<(crate::TokenStream, crate::TokenStream), crate::TokenStream
             run,
             force_show_panics,
         )
-        .map(<MarkedTypes<S> as Types>::TokenStream::unmark)
+        .map(|s| <Option<<MarkedTypes<S> as Types>::TokenStream>>::unmark(s).unwrap_or_default())
     }
 }