diff --git a/erlang/apps/sim/src/sim_core.erl b/erlang/apps/sim/src/sim_core.erl
index d241cda..258835e 100644
--- a/erlang/apps/sim/src/sim_core.erl
+++ b/erlang/apps/sim/src/sim_core.erl
@@ -229,6 +229,7 @@ dispatch(Core, Mem, IR, EA) ->
     8#202 -> sim_moves:handle_MOVEM(Core, Mem, IR, EA);
     8#203 -> sim_moves:handle_MOVES(Core, Mem, IR, EA);
     8#204 -> sim_moves:handle_MOVS(Core, Mem, IR, EA);
+    8#205 -> sim_moves:handle_MOVSI(Core, Mem, IR, EA);
     8#250 -> sim_moves:handle_EXCH(Core, Mem, IR, EA);
     _ ->
       PC = (Core#core.pc_section bsl 18) bor Core#core.pc_offset,
diff --git a/erlang/apps/sim/src/sim_moves.erl b/erlang/apps/sim/src/sim_moves.erl
index f52bd47..2fe5d50 100644
--- a/erlang/apps/sim/src/sim_moves.erl
+++ b/erlang/apps/sim/src/sim_moves.erl
@@ -30,6 +30,7 @@
         , handle_MOVEM/4
         , handle_MOVES/4
         , handle_MOVS/4
+        , handle_MOVSI/4
         ]).
 
 -include("sim_core.hrl").
@@ -131,6 +132,12 @@ handle_MOVS(Core, Mem, IR, EA) ->
                           fun(Core1, Mem1) -> handle_MOVS(Core1, Mem1, IR, EA) end)
   end.
 
+-spec handle_MOVSI(#core{}, sim_mem:mem(), IR :: word(), #ea{})
+      -> {#core{}, sim_mem:mem(), {ok, integer()} | {error, {module(), term()}}}.
+handle_MOVSI(Core, Mem, IR, #ea{offset = E}) ->
+  AC = IR band 8#17,
+  sim_core:next_pc(sim_core:set_ac(Core, AC, E bsl 18), Mem).
+
 %% Miscellaneous ===============================================================
 
 ea_address(#ea{section = Section, offset = Offset}) ->
diff --git a/erlang/apps/sim/test/sim_moves_tests.erl b/erlang/apps/sim/test/sim_moves_tests.erl
index 30d239f..7c4d68f 100644
--- a/erlang/apps/sim/test/sim_moves_tests.erl
+++ b/erlang/apps/sim/test/sim_moves_tests.erl
@@ -48,6 +48,7 @@
 -define(OP_MOVEM, 8#202).
 -define(OP_MOVES, 8#203).
 -define(OP_MOVS, 8#204).
+-define(OP_MOVSI, 8#205).
 -define(OP_EXCH, 8#250).
 
 %% 2.1.1 Exchange Instruction ==================================================
@@ -144,6 +145,15 @@ movs_test() ->
          [ {#ea{section = 1, offset = 1, islocal = false}, ?COMMA2(8#42, 8#27)} % AC1 = 42,,27
          ]).
 
+movsi_test() ->
+  Prog =
+    [ {1, 8#100, ?INSN(?OP_MOVSI, 1, 0, 0, -1)}     % 1,,100/ MOVSI 1,-1
+    , {1, 8#101, ?INSN_INVALID}                     % 1,,101/ <invalid>
+    ],
+  expect(Prog, [], {1, 8#101}, ?DEFAULT_FLAGS,
+         [ {#ea{section = 1, offset = 1, islocal = false}, ?COMMA2(-1, 0)} % AC1 = -1,,0
+         ]).
+
 %% Common code to run short sequences ==========================================
 
 expect(Prog, ACs, ExpectedPC, ExpectedFlags, ExpectedEs) ->