diff --git a/compiler.py b/compiler.py
index 5a7eb57..7431207 100644
--- a/compiler.py
+++ b/compiler.py
@@ -554,13 +554,13 @@ def temp_addr(self, x: Union[Var, Struct], *, is_head: bool = False) -> Tuple[Re
             # Conflict avoidance: do not use registers that are necessary for last goal args.
             no_use = no_use | self.conflict[x]
 
-        addr = self.alloc_reg(x, use, no_use)
+        addr = self.alloc_reg(use, no_use)
         self.set_reg(addr, x)
 
         alloc = AddrAlloc.NEW_VAR if isinstance(x, Var) else AddrAlloc.NEW_STRUCT
         return addr, alloc
 
-    def alloc_reg(self, x: Union[Var, Struct], use: Set[Register], no_use: Set[Register]) -> Register:
+    def alloc_reg(self, use: Set[Register], no_use: Set[Register]) -> Register:
         """Allocate a register for a variable or struct."""
         # Try to allocate a free register.
         free = self.free_regs & use