diff --git a/legate/core/context.py b/legate/core/context.py
index 63c4beb1dc..069fca9b69 100644
--- a/legate/core/context.py
+++ b/legate/core/context.py
@@ -370,7 +370,13 @@ def issue_execution_fence(self, block: bool = False) -> None:
         """
         self._runtime.issue_execution_fence(block=block)
 
-    def tree_reduce(self, task_id: int, store: Store, radix: int = 4) -> Store:
+    def tree_reduce(
+        self,
+        task_id: int,
+        store: Store,
+        radix: int = 4,
+        scalar_args: list[tuple[Any, Dtype]] = [],
+    ) -> Store:
         """
         Performs a user-defined reduction by building a tree of reduction
         tasks. At each step, the reducer task gets up to ``radix`` input stores
@@ -399,4 +405,6 @@ def tree_reduce(self, task_id: int, store: Store, radix: int = 4) -> Store:
         Store
             Store that contains reduction results
         """
-        return self._runtime.tree_reduce(self, task_id, store, radix)
+        return self._runtime.tree_reduce(
+            self, task_id, store, radix, scalar_args
+        )
diff --git a/legate/core/operation.py b/legate/core/operation.py
index 2483cadfb1..ea493fe523 100644
--- a/legate/core/operation.py
+++ b/legate/core/operation.py
@@ -1494,6 +1494,7 @@ def __init__(
         )
         self._radix = radix
         self._task_id = task_id
+        self._scalar_args: list[tuple[Any, ty.Dtype]] = []
 
     def add_input(self, store: Store) -> None:
         self._check_store(store)
@@ -1508,6 +1509,9 @@ def add_output(self, store: Store) -> None:
         self._outputs.append(store)
         self._output_parts.append(partition)
 
+    def add_scalar_arg(self, value: Any, dtype: ty.Dtype) -> None:
+        self._scalar_args.append((value, dtype))
+
     def launch(self, strategy: Strategy) -> None:
         assert len(self._inputs) == 1 and len(self._outputs) == 1
 
@@ -1537,6 +1541,9 @@ def launch(self, strategy: Strategy) -> None:
                 provenance=self.provenance,
             )
 
+            for scalar, dtype in self._scalar_args:
+                launcher.add_scalar_arg(scalar, dtype)
+
             if num_tasks > 1:
                 for proj_fn in proj_fns:
                     launcher.add_input(
diff --git a/legate/core/runtime.py b/legate/core/runtime.py
index 0aca17e5a6..96ca2f0712 100644
--- a/legate/core/runtime.py
+++ b/legate/core/runtime.py
@@ -1731,7 +1731,12 @@ def issue_fill(
         fill.execute()
 
     def tree_reduce(
-        self, context: Context, task_id: int, store: Store, radix: int = 4
+        self,
+        context: Context,
+        task_id: int,
+        store: Store,
+        radix: int = 4,
+        scalar_args: list[tuple[Any, ty.Dtype]] = [],
     ) -> Store:
         """
         Performs a user-defined reduction by building a tree of reduction
@@ -1780,6 +1785,8 @@ def tree_reduce(
         )
         task.add_input(store)
         task.add_output(result)
+        for scalar_arg in scalar_args:
+            task.add_scalar_arg(scalar_arg[0], scalar_arg[1])
         task.execute()
         return result