diff --git a/tools/cc.py b/tools/cc.py
index 42c784d..ac70e2c 100644
--- a/tools/cc.py
+++ b/tools/cc.py
@@ -386,6 +386,14 @@ class Incr(UnOp):
                 f'add {self.dest}, {self.operand}, {sc0}',
                 f'or {self.operand}, {self.dest}, {self.dest}']
 
+class Decr(UnOp):
+    scratch_need = 1
+    def synth(self, scratches):
+        sc0 = scratches[0]
+        return [f'set {sc0}, 1',
+                f'sub {self.dest}, {self.operand}, {sc0}',
+                f'or {self.operand}, {self.dest}, {self.dest}']
+
 
 class NotOp(UnOp):
     def synth(self, scratches):
@@ -853,6 +861,14 @@ class CcInterp(lark.visitors.Interpreter):
         self.cur_fun.deferred_ops.append(Incr(self.cur_fun, [reg, reg]))
         self.cur_fun.deferred_ops.append(Store(self.cur_fun, [reg, var]))
 
+    def post_decrement(self, tree):
+        self.visit_children(tree)
+        tree.op = Reg(tree.children[0].op.out)
+        var = tree.children[0].var
+        reg = tree.op.out
+        self.cur_fun.deferred_ops.append(Decr(self.cur_fun, [reg, reg]))
+        self.cur_fun.deferred_ops.append(Store(self.cur_fun, [reg, var]))
+
     pre_increment = _unary_op(Incr)
     bool_not = _unary_op(BoolNot)