diff --git a/test/construct.test.did b/test/construct.test.did
index d516b281..290f0cbe 100644
--- a/test/construct.test.did
+++ b/test/construct.test.did
@@ -62,11 +62,6 @@ assert blob "DIDL\01\6d\00\01\00\02\00\00" == "(vec { vec {}; vec {} })"    : (V
 assert blob "DIDL\01\6d\00\01\00\02\00\00" == "(vec { vec {}; vec {} })"    : (vec vec opt empty) "vec: non-recursive tree";
 assert blob "DIDL\01\6d\7f\01\00\e8\07"                                     : (vec null) "vec null";
 assert blob "DIDL\01\6d\7f\01\00\e8\07"                                     : (vec opt nat) "vec null <: vec opt nat";
-assert blob "DIDL\01\6d\7f\01\00\80\94\eb\dc\03"                           !: (vec opt nat) "space bomb: vec null <: vec opt nat";
-assert blob "DIDL\01\6d\70\01\00\80\94\eb\dc\03"                           !: (opt nat) "space bomb: send vec reserved to opt nat";
-assert blob "DIDL\04\6c\03\01\7f\02\01\03\02\6c\01\01\70\6c\00\6d\00\01\03\80\94\eb\dc\03" !: (vec record {null;record{reserved};record{}}) "space bomb: zero-sized record";
-assert blob "DIDL\02\6d\01\6d\7f\01\00\05\ff\ff\3f\ff\ff\3f\ff\ff\3f\ff\ff\3f\ff\ff\3f"    !: (vec vec null) "space bomb: vec vec null";
-assert blob "DIDL\03\6c\01\d6\fc\a7\02\01\6d\02\6c\00\01\00\80\ad\e2\04"                   !: (vec record {}) "space bomb: vec record {}";
 assert "(vec { 1; -1 })"                                                   !: (vec nat) "vec: type mismatch";
 assert blob "DIDL\01\6d\7c\01\00"                                          !: (vec int) "vec: too short";
 assert blob "DIDL\01\6d\7c\01\00\02\01"                                    !: (vec int) "vec: too short";
diff --git a/test/spacebomb.test.did b/test/spacebomb.test.did
new file mode 100644
index 00000000..5c2d415c
--- /dev/null
+++ b/test/spacebomb.test.did
@@ -0,0 +1,47 @@
+
+// Space bomb tests
+
+
+// Messages with more than 2_000_000 zero-length elements in vectors should be rejected
+
+// \80\94\eb\dc\03  is 1000_000_000
+// \80\ad\e2\04     is   10_000_000
+// \80\89\7a        is    2_000_000
+// \ff\ff\3f        is    1_048_575
+// \80\b5\18        is      400_000
+
+
+// Plain decoding (unused arguments) 
+assert blob "DIDL\01\6d\7f\01\00\80\94\eb\dc\03"                           !: () "vec null (extra argument)";
+assert blob "DIDL\01\6d\70\01\00\80\94\eb\dc\03"                           !: () "vec reserved (extra argument)";
+assert blob "DIDL\04\6c\03\01\7f\02\01\03\02\6c\01\01\70\6c\00\6d\00\01\03\80\94\eb\dc\03" !: () "zero-sized record (extra argument)";
+assert blob "DIDL\02\6d\01\6d\7f\01\00\05\ff\ff\3f\ff\ff\3f\ff\ff\3f\ff\ff\3f\ff\ff\3f"    !: () "vec vec null (extra argument)";
+assert blob "DIDL\03\6c\01\d6\fc\a7\02\01\6d\02\6c\00\01\00\80\ad\e2\04"                   !: () "vec record {} (extra argument)";
+
+// Messages with exactly 2_000_000 zero-length elements should succeed
+assert blob "DIDL\01\6d\7f\01\00\80\89\7a"                           : () "vec null (exactly 2000000)";
+assert blob "DIDL\01\6d\70\01\00\80\89\7a"                           : () "vec reserved (exactly 2000000)";
+assert blob "DIDL\04\6c\03\01\7f\02\01\03\02\6c\01\01\70\6c\00\6d\00\01\03\80\89\7a" : () "zero-sized record (exactly 2000000)";
+assert blob "DIDL\02\6d\01\6d\7f\01\00\05\80\b5\18\80\b5\18\80\b5\18\80\b5\18\80\b5\18" : () "vec vec null (exactly 2000000)";
+assert blob "DIDL\03\6c\01\d6\fc\a7\02\01\6d\02\6c\00\01\00\80\89\7a"                   : () "vec record {} (exactly 2000000)";
+
+// Messages with exactly 2_000_001 zero-length elements should fail
+assert blob "DIDL\01\6d\7f\01\00\80\89\7b"                           !: () "vec null (exactly 2000001)";
+assert blob "DIDL\01\6d\70\01\00\80\89\7b"                           !: () "vec reserved (exactly 2000001)";
+assert blob "DIDL\04\6c\03\01\7f\02\01\03\02\6c\01\01\70\6c\00\6d\00\01\03\80\89\7b" !: () "zero-sized record (exactly 2000001)";
+assert blob "DIDL\02\6d\01\6d\7f\01\00\05\80\b5\18\80\b5\18\80\b5\18\80\b5\18\80\b5\19" !: () "vec vec null (exactly 2000001)";
+assert blob "DIDL\03\6c\01\d6\fc\a7\02\01\6d\02\6c\00\01\00\80\89\7b"                   !: () "vec record {} (exactly 2000001)";
+
+// Decoding to actual type
+assert blob "DIDL\01\6d\7f\01\00\80\94\eb\dc\03"                           !: (vec opt nat) "vec null (not ignored)";
+assert blob "DIDL\01\6d\70\01\00\80\94\eb\dc\03"                           !: (vec reserved) "vec reserved (not ignored)";
+assert blob "DIDL\04\6c\03\01\7f\02\01\03\02\6c\01\01\70\6c\00\6d\00\01\03\80\94\eb\dc\03" !: (vec record {null;record{reserved};record{}}) "zero-sized record (not ignored)";
+assert blob "DIDL\02\6d\01\6d\7f\01\00\05\ff\ff\3f\ff\ff\3f\ff\ff\3f\ff\ff\3f\ff\ff\3f"    !: (vec vec null) "vec vec null (not ignored)";
+assert blob "DIDL\03\6c\01\d6\fc\a7\02\01\6d\02\6c\00\01\00\80\ad\e2\04"                   !: (vec record {}) "vec record {} (not ignored)";
+
+// Decoding under opt
+assert blob "DIDL\01\6d\7f\01\00\80\94\eb\dc\03"                           !: (opt nat) "vec null (subtyping)";
+assert blob "DIDL\01\6d\70\01\00\80\94\eb\dc\03"                           !: (opt nat) "vec reserved (subtyping)";
+assert blob "DIDL\04\6c\03\01\7f\02\01\03\02\6c\01\01\70\6c\00\6d\00\01\03\80\94\eb\dc\03" !: (opt nat) "zero-sized record (subtyping)";
+assert blob "DIDL\02\6d\01\6d\7f\01\00\05\ff\ff\3f\ff\ff\3f\ff\ff\3f\ff\ff\3f\ff\ff\3f"    !: (vec opt nat) "vec vec null (subtyping)";
+assert blob "DIDL\03\6c\01\d6\fc\a7\02\01\6d\02\6c\00\01\00\80\ad\e2\04"                   !: (opt nat) "vec record {} (subtyping)";