diff --git a/xls/scheduling/scheduling_options.cc b/xls/scheduling/scheduling_options.cc
index 4d04f37c28..479d99133b 100644
--- a/xls/scheduling/scheduling_options.cc
+++ b/xls/scheduling/scheduling_options.cc
@@ -39,7 +39,7 @@ namespace xls {
 namespace {
 
 absl::StatusOr<SchedulingOptions> OptionsFromFlagProto(
-    Package* p, const SchedulingOptionsFlagsProto& proto) {
+    const Package* p, const SchedulingOptionsFlagsProto& proto) {
   // Some fields are pre-initialized with defaults
   SchedulingOptions scheduling_options;
 
@@ -297,7 +297,7 @@ absl::StatusOr<bool> IsDelayModelSpecifiedViaFlag(
 }
 
 absl::StatusOr<SchedulingOptions> SetUpSchedulingOptions(
-    const SchedulingOptionsFlagsProto& flags, Package* p) {
+    const SchedulingOptionsFlagsProto& flags, const Package* p) {
   return OptionsFromFlagProto(p, flags);
 }
 
diff --git a/xls/scheduling/scheduling_options.h b/xls/scheduling/scheduling_options.h
index b6e431db3e..3a6afd186b 100644
--- a/xls/scheduling/scheduling_options.h
+++ b/xls/scheduling/scheduling_options.h
@@ -636,7 +636,7 @@ class SchedulingOptions {
 using ScheduleCycleMap = absl::flat_hash_map<Node*, int64_t>;
 
 absl::StatusOr<SchedulingOptions> SetUpSchedulingOptions(
-    const SchedulingOptionsFlagsProto& flags, Package* p);
+    const SchedulingOptionsFlagsProto& flags, const Package* p);
 
 absl::StatusOr<DelayEstimator*> SetUpDelayEstimator(
     const SchedulingOptionsFlagsProto& flags);