diff --git a/erlang/apps/sim/src/sim_boolean.erl b/erlang/apps/sim/src/sim_boolean.erl
index 207dae0..f926cb9 100644
--- a/erlang/apps/sim/src/sim_boolean.erl
+++ b/erlang/apps/sim/src/sim_boolean.erl
@@ -31,6 +31,7 @@
         , handle_ANDCAI/4
         , handle_ANDCAM/4
         , handle_ANDCM/4
+        , handle_ANDCMI/4
         , handle_ANDI/4
         , handle_ANDM/4
         , handle_SETMB/4
@@ -250,6 +251,14 @@ handle_ANDCM(Core, Mem, IR, EA) ->
                           fun(Core1, Mem1) -> handle_ANDCM(Core1, Mem1, IR, EA) end)
   end.
 
+-spec handle_ANDCMI(#core{}, sim_mem:mem(), IR :: word(), #ea{})
+      -> {#core{}, sim_mem:mem(), {ok, integer()} | {error, {module(), term()}}}.
+handle_ANDCMI(Core, Mem, IR, EA) ->
+  AC = IR band 8#17,
+  CA = sim_core:get_ac(Core, AC),
+  Word = CA band bnot EA#ea.offset,
+  sim_core:next_pc(sim_core:set_ac(Core, AC, Word), Mem).
+
 %% Miscellaneous ===============================================================
 
 ea_address(#ea{section = Section, offset = Offset}) ->
diff --git a/erlang/apps/sim/src/sim_core.erl b/erlang/apps/sim/src/sim_core.erl
index 2135e99..097cd67 100644
--- a/erlang/apps/sim/src/sim_core.erl
+++ b/erlang/apps/sim/src/sim_core.erl
@@ -270,6 +270,7 @@ dispatch(Core, Mem, IR, EA) ->
     8#416 -> sim_boolean:handle_SETMM(Core, Mem, IR, EA);
     8#417 -> sim_boolean:handle_SETMB(Core, Mem, IR, EA);
     8#420 -> sim_boolean:handle_ANDCM(Core, Mem, IR, EA);
+    8#421 -> sim_boolean:handle_ANDCMI(Core, Mem, IR, EA);
     _ ->
       PC = (Core#core.pc_section bsl 18) bor Core#core.pc_offset,
       {Core, Mem, {error, {?MODULE, {dispatch, PC, IR, EA}}}}
diff --git a/erlang/apps/sim/test/sim_boolean_tests.erl b/erlang/apps/sim/test/sim_boolean_tests.erl
index 526f3c3..e7e3f49 100644
--- a/erlang/apps/sim/test/sim_boolean_tests.erl
+++ b/erlang/apps/sim/test/sim_boolean_tests.erl
@@ -61,6 +61,7 @@
 -define(OP_SETMM, 8#416).
 -define(OP_SETMB, 8#417).
 -define(OP_ANDCM, 8#420).
+-define(OP_ANDCMI, 8#421).
 
 %% 2.4 Boolean Functions =======================================================
 
@@ -298,6 +299,16 @@ andcm_test() ->
          [ {#ea{section = 1, offset = 1, islocal = false}, ?COMMA2(0, 8#030303)} % AC1 = 0,,030303
          ]).
 
+andcmi_test() ->
+  Prog =
+    [ {1, 8#100, ?INSN(?OP_MOVEI, 1, 0, 0, 8#333333)}  % 1,,100/ MOVEI 1,333333
+    , {1, 8#101, ?INSN(?OP_ANDCMI, 1, 0, 0, 8#707070)} % 1,,101/ ANDCMI 1,707070
+    , {1, 8#102, ?INSN_INVALID}                        % 1,,102/ <invalid>
+    ],
+  expect(Prog, [], {1, 8#102}, ?DEFAULT_FLAGS,
+         [ {#ea{section = 1, offset = 1, islocal = false}, 8#030303} % AC1 = 0,,030303
+         ]).
+
 %% Common code to run short sequences ==========================================
 
 expect(Prog, ACs, ExpectedPC, ExpectedFlags, ExpectedEs) ->