diff --git a/scripts/update_asm_instructions.py b/scripts/update_asm_instructions.py
index bbb06d5..94f9608 100755
--- a/scripts/update_asm_instructions.py
+++ b/scripts/update_asm_instructions.py
@@ -266,6 +266,16 @@ class Instruction(object):
 
         return ret
 
+    def _handle_null_case(self, case):
+        """
+        Return code to handle an instruction case that takes no arguments.
+        """
+        return [
+            TAB + "if (INST_NARGS == 0) {",
+            self._handle_return(case["return"], 2),
+            TAB + "}"
+        ]
+
     def _handle_pseudo_case(self, pseudo, case):
         """
         Return code to handle an instruction pseudo-case.
@@ -294,6 +304,9 @@ class Instruction(object):
         Return code to handle an instruction case.
         """
         ctype = case["type"]
+        if not ctype:
+            return self._handle_null_case(case)
+
         for pseudo in self.PSEUDO_TYPES:
             if pseudo in ctype:
                 return self._handle_pseudo_case(pseudo, case)
diff --git a/src/assembler/instructions.c b/src/assembler/instructions.c
index ac2558f..04e0cea 100644
--- a/src/assembler/instructions.c
+++ b/src/assembler/instructions.c
@@ -65,8 +65,6 @@ static ASMErrorDesc parse_inst_##mnemonic(                                    \
         INST_ERROR(TOO_MANY_ARGS)
 
 #define INST_TAKES_ARGS(a0, a1, a2)                                           \
-    if (!ap_info.arg)                                                         \
-        INST_ERROR(TOO_FEW_ARGS)                                              \
     ASMInstArg args[3];                                                       \
     size_t nargs;                                                             \
     ASMArgType masks[] = {a0, a1, a2};                                        \
diff --git a/src/assembler/instructions.inc.c b/src/assembler/instructions.inc.c
index c368a00..3e3ce2a 100644
--- a/src/assembler/instructions.inc.c
+++ b/src/assembler/instructions.inc.c
@@ -7,7 +7,7 @@
     `make` should trigger a rebuild when it is modified; if not, use:
     `python scripts/update_asm_instructions.py`.
 
-    @AUTOGEN_DATE Wed May 20 06:40:09 2015 UTC
+    @AUTOGEN_DATE Wed May 20 06:53:00 2015 UTC
 */
 
 /* @AUTOGEN_INST_BLOCK_START */
@@ -1652,6 +1652,38 @@ INST_FUNC(res)
     INST_ERROR(ARG_TYPE)
 }
 
+INST_FUNC(ret)
+{
+    INST_TAKES_ARGS(
+        AT_CONDITION|AT_OPTIONAL,
+        AT_NONE,
+        AT_NONE
+    )
+    if (INST_NARGS == 0) {
+        INST_RETURN(1, 0xC9)
+    }
+    if (INST_NARGS == 1 && INST_TYPE(0) == AT_CONDITION) {
+        if (INST_COND(0) == COND_NZ)
+            INST_RETURN(1, 0xC0)
+        if (INST_COND(0) == COND_Z)
+            INST_RETURN(1, 0xC8)
+        if (INST_COND(0) == COND_NC)
+            INST_RETURN(1, 0xD0)
+        if (INST_COND(0) == COND_C)
+            INST_RETURN(1, 0xD8)
+        if (INST_COND(0) == COND_PO)
+            INST_RETURN(1, 0xE0)
+        if (INST_COND(0) == COND_PE)
+            INST_RETURN(1, 0xE8)
+        if (INST_COND(0) == COND_P)
+            INST_RETURN(1, 0xF0)
+        if (INST_COND(0) == COND_M)
+            INST_RETURN(1, 0xF8)
+        INST_ERROR(ARG_VALUE)
+    }
+    INST_ERROR(ARG_TYPE)
+}
+
 INST_FUNC(reti)
 {
     INST_TAKES_NO_ARGS
@@ -2032,6 +2064,7 @@ static ASMInstParser lookup_parser(uint32_t key)
     HANDLE(pop)
     HANDLE(push)
     HANDLE(res)
+    HANDLE(ret)
     HANDLE(reti)
     HANDLE(retn)
     HANDLE(rla)
diff --git a/src/assembler/instructions.yml b/src/assembler/instructions.yml
index 6815608..ad68719 100644
--- a/src/assembler/instructions.yml
+++ b/src/assembler/instructions.yml
@@ -1110,9 +1110,29 @@ res:
             - cond:   [bit.7, _, l]
               return: [0xCB, 0xBD]
 
-# ret:
-#     args: yes
-#     return: TODO
+ret:
+    args: yes
+    cases:
+        - type: []
+          return: [0xC9]
+        - type: [condition]
+          cases:
+            - cond:   [nz]
+              return: [0xC0]
+            - cond:   [z]
+              return: [0xC8]
+            - cond:   [nc]
+              return: [0xD0]
+            - cond:   [c]
+              return: [0xD8]
+            - cond:   [po]
+              return: [0xE0]
+            - cond:   [pe]
+              return: [0xE8]
+            - cond:   [p]
+              return: [0xF0]
+            - cond:   [m]
+              return: [0xF8]
 
 reti:
     args: no