diff --git a/src/backend_x64/reg_alloc.cpp b/src/backend_x64/reg_alloc.cpp
index a56de6ca..889d92ac 100644
--- a/src/backend_x64/reg_alloc.cpp
+++ b/src/backend_x64/reg_alloc.cpp
@@ -130,7 +130,7 @@ std::tuple<OpArg, HostLoc> RegAlloc::UseDefOpArgHostLocReg(IR::Value use_value,
     DEBUG_ASSERT_MSG(use_value.IsImmediate() || ValueLocation(use_value.GetInst()), "use_inst has not been defined");
 
     if (!use_value.IsImmediate()) {
-        IR::Inst* use_inst = use_value.GetInst();
+        const IR::Inst* use_inst = use_value.GetInst();
 
         if (IsLastUse(use_inst)) {
             HostLoc current_location = *ValueLocation(use_inst);
@@ -347,7 +347,7 @@ bool RegAlloc::IsRegisterAllocated(HostLoc loc) const {
     return LocInfo(loc).is_being_used;
 }
 
-bool RegAlloc::IsLastUse(IR::Inst* inst) const {
+bool RegAlloc::IsLastUse(const IR::Inst* inst) const {
     if (inst->use_count > 1)
         return false;
     return LocInfo(*ValueLocation(inst)).values.size() == 1;
diff --git a/src/backend_x64/reg_alloc.h b/src/backend_x64/reg_alloc.h
index faae4cf5..648ccd58 100644
--- a/src/backend_x64/reg_alloc.h
+++ b/src/backend_x64/reg_alloc.h
@@ -156,7 +156,7 @@ private:
     boost::optional<HostLoc> ValueLocation(const IR::Inst* value) const;
     bool IsRegisterOccupied(HostLoc loc) const;
     bool IsRegisterAllocated(HostLoc loc) const;
-    bool IsLastUse(IR::Inst* inst) const;
+    bool IsLastUse(const IR::Inst* inst) const;
 
     HostLoc DefHostLocReg(IR::Inst* def_inst, HostLocList desired_locations);
     HostLoc UseDefHostLocReg(IR::Value use_value, IR::Inst* def_inst, HostLocList desired_locations);