diff --git a/py65/assembler.py b/py65/assembler.py
index 8d07ccf..d513082 100644
--- a/py65/assembler.py
+++ b/py65/assembler.py
@@ -55,6 +55,7 @@ class Assembler:
             match = pattern.match(operand)
 
             if match:
+                # check if opcode supports this addressing mode
                 try:
                     bytes = [self._mpu.disassemble.index((opcode, mode))]
                 except ValueError:
@@ -98,9 +99,16 @@ class Assembler:
         if match:
             before, target, after = match.groups()
 
-            # target is an immediate number
+            # target is an immediate value
             if target.startswith('#'):
-                number = self._address_parser.number(target[1:])
+                if target[1] in ("'", '"'): # quoted ascii character
+                    try:
+                        number = ord(target[2])
+                    except IndexError:
+                        raise SyntaxError(statement)
+                else:
+                    number = self._address_parser.number(target[1:])
+
                 if (number < 0x00) or (number > self._mpu.byteMask):
                     raise OverflowError
                 statement = before + '#$' + self._mpu.BYTE_FORMAT % number
diff --git a/py65/tests/test_assembler.py b/py65/tests/test_assembler.py
index f47ef15..9eb7b81 100644
--- a/py65/tests/test_assembler.py
+++ b/py65/tests/test_assembler.py
@@ -22,6 +22,8 @@ class AssemblerTests(unittest.TestCase):
     def test_assemble_bad_syntax_raises_syntaxerror(self):
         self.assertRaises(SyntaxError,
                           self.assemble, 'foo')
+        self.assertRaises(SyntaxError,
+                          self.assemble, 'lda #"')
 
     def test_assemble_bad_label_raises_keyerror(self):
         self.assertRaises(KeyError,
@@ -820,6 +822,12 @@ class AssemblerTests(unittest.TestCase):
         self.assertEqual([0xa9, 0x44],
                          self.assemble('LDA #$44'))
 
+    def test_assembles_a9_ascii(self):
+        self.assertEqual([0xa9, 0x48],
+                         self.assemble("LDA #'H"))
+        self.assertEqual([0xa9, 0x49],
+                         self.assemble('LDA #"I'))
+
     def test_assembles_aa(self):
         self.assertEqual([0xaa],
                          self.assemble('TAX'))