diff --git a/py65/devices/mpu65c02.py b/py65/devices/mpu65c02.py
index ef37f74..7e52839 100644
--- a/py65/devices/mpu65c02.py
+++ b/py65/devices/mpu65c02.py
@@ -167,7 +167,7 @@ class MPU(mpu6502.MPU):
     def inst_0x5a(self):
         self.stPush(self.y)
 
-    @instruction(name="STZ", mode="imp", cycles=3)
+    @instruction(name="STZ", mode="zpg", cycles=3)
     def inst_0x64(self):
         self.opSTZ(self.ZeroPageAddr)
         self.pc += 1
diff --git a/py65/disassembler.py b/py65/disassembler.py
index 9b8caf8..af02e30 100644
--- a/py65/disassembler.py
+++ b/py65/disassembler.py
@@ -102,8 +102,8 @@ class Disassembler:
         elif addressing == 'zpi':
             zp_address = self._mpu.ByteAt(pc + 1)
             address_or_label = self._address_parser.label_for(
-                zp_address, '($' + self.byteFmt % zp_address + ')')
-            disasm += ' %s' % address_or_label
+                zp_address, '$' + self.byteFmt % zp_address)
+            disasm += ' (%s)' % address_or_label
             length = 2
 
         elif addressing == 'zpg':
diff --git a/py65/tests/test_assembler.py b/py65/tests/test_assembler.py
index a4715b1..d256778 100644
--- a/py65/tests/test_assembler.py
+++ b/py65/tests/test_assembler.py
@@ -501,8 +501,8 @@ class AssemblerTests(unittest.TestCase):
 
     def test_assembles_64_65c02(self):
         mpu = MPU65C02()
-        self.assertEqual([0x64],
-                         self.assemble('STZ', 0x0000, mpu))
+        self.assertEqual([0x64, 0x12],
+                         self.assemble('STZ $12', 0x0000, mpu))
 
     def test_assembles_65(self):
         self.assertEqual([0x65, 0x44],