diff --git a/TKET_VERSION b/TKET_VERSION
index f674781b93..0228499b2d 100644
--- a/TKET_VERSION
+++ b/TKET_VERSION
@@ -1 +1 @@
-2.1.79
+2.1.80
diff --git a/pytket/binders/circuit/Circuit/add_op.cpp b/pytket/binders/circuit/Circuit/add_op.cpp
index 3c49ac21d2..ba151d9ca3 100644
--- a/pytket/binders/circuit/Circuit/add_op.cpp
+++ b/pytket/binders/circuit/Circuit/add_op.cpp
@@ -146,6 +146,29 @@ Circuit *add_gate_method_any(
       }
     }
   }
+
+  // check if there are wasm wires in the signature
+
+  op_signature_t sig = new_op->get_signature();
+
+  unsigned count_wasm_sig = 0;
+  for (EdgeType e : sig) {
+    if (e == EdgeType::WASM) {
+      ++count_wasm_sig;
+    }
+  }
+
+  unsigned count_wasm_args = 0;
+  for (UnitID uid : new_args) {
+    if (uid.type() == UnitType::WasmState) {
+      ++count_wasm_args;
+    }
+  }
+
+  if (count_wasm_args != count_wasm_sig) {
+    new_args.push_back(WasmState(0));
+  }
+
   circ->add_op(new_op, new_args, opgroup);
   return circ;
 }
@@ -577,6 +600,29 @@ void init_circuit_add_op(nb::class_<Circuit> &c) {
                 args.push_back(Bit(name, i));
               }
             }
+
+            // check if there are wasm wires in the signature
+
+            op_signature_t sig = box.get_signature();
+
+            unsigned count_wasm_sig = 0;
+            for (EdgeType e : sig) {
+              if (e == EdgeType::WASM) {
+                ++count_wasm_sig;
+              }
+            }
+
+            unsigned count_wasm_args = 0;
+            for (UnitID uid : args) {
+              if (uid.type() == UnitType::WasmState) {
+                ++count_wasm_args;
+              }
+            }
+
+            if (count_wasm_args != count_wasm_sig) {
+              args.push_back(WasmState(0));
+            }
+
             return add_gate_method_any(
                 circ, std::make_shared<CircBox>(box), args, kwargs);
           },
diff --git a/pytket/docs/changelog.md b/pytket/docs/changelog.md
index 5bcc436670..8e22473c95 100644
--- a/pytket/docs/changelog.md
+++ b/pytket/docs/changelog.md
@@ -1,5 +1,10 @@
 # Changelog
 
+# 2.17.0 (April 2026)
+
+Fixes:
+- Fix handling of wasm function calls in circuit boxes 
+
 ## 2.16.0 (March 2026)
 
 Features:
diff --git a/pytket/tests/classical_test.py b/pytket/tests/classical_test.py
index 47f6f9850d..64e9431e96 100644
--- a/pytket/tests/classical_test.py
+++ b/pytket/tests/classical_test.py
@@ -69,7 +69,7 @@
     reg_lt,
     reg_neq,
 )
-from pytket.passes import DecomposeClassicalExp
+from pytket.passes import DecomposeBoxes, DecomposeClassicalExp
 
 curr_file_path = Path(__file__).resolve().parent
 
@@ -904,6 +904,27 @@ def test_wasm_circuit_bits() -> None:
 DrawType = Callable[[SearchStrategy[T]], T]
 
 
+def test_wasm_box() -> None:
+
+    wasm_module = wasm.WasmFileHandler("testfile.wasm")
+
+    A = BitRegister("A", 1)
+    B = BitRegister("B", 1)
+
+    c0 = Circuit()
+    c0.add_c_register(A)
+    c0.add_c_register(B)
+    c0.add_wasm_to_reg("add_one", wasm_module, [A], [B])
+    c0box = CircBox(c0)
+
+    c1 = Circuit()
+    c1.add_c_register(A)
+    c1.add_c_register(B)
+    c1.add_circbox_regwise(c0box, qregs=[], cregs=[A, B])
+
+    DecomposeBoxes().apply(c1)
+
+
 @strategies.composite
 def bit_register(
     draw: DrawType,
diff --git a/pytket/tests/transform_test.py b/pytket/tests/transform_test.py
index e6fae1f32d..a47277a3e2 100644
--- a/pytket/tests/transform_test.py
+++ b/pytket/tests/transform_test.py
@@ -1621,7 +1621,8 @@ def iregs(name: str, size: int) -> str:
         iregs("bound", 32)
         + iregs("index", 32)
         + iregs("num", 32)
-        + iregs("seed", 64)[:-2]
+        + iregs("seed", 64)
+        + iregs("_w", 1)[:-2]
         + ";"
     )
     cmds = c.get_commands()
diff --git a/tket/src/Circuit/Boxes.cpp b/tket/src/Circuit/Boxes.cpp
index fa8151c4be..60e7802666 100644
--- a/tket/src/Circuit/Boxes.cpp
+++ b/tket/src/Circuit/Boxes.cpp
@@ -82,7 +82,9 @@ CircBox::CircBox(const Circuit &circ) : Box(OpType::CircBox) {
   }
   signature_ = op_signature_t(circ.n_qubits(), EdgeType::Quantum);
   op_signature_t bits(circ.n_bits(), EdgeType::Classical);
+  op_signature_t wasmwire(circ._number_of_wasm_wires, EdgeType::WASM);
   signature_.insert(signature_.end(), bits.begin(), bits.end());
+  signature_.insert(signature_.end(), wasmwire.begin(), wasmwire.end());
   circ_ = std::make_shared<Circuit>(circ);
 }
 
diff --git a/tket/test/src/test_wasm.cpp b/tket/test/src/test_wasm.cpp
index e3f884737d..19f0d369c5 100644
--- a/tket/test/src/test_wasm.cpp
+++ b/tket/test/src/test_wasm.cpp
@@ -228,7 +228,12 @@ SCENARIO("generating circ with wasm") {
 
     CircBox circbox(u);
     Circuit major_circ(0, 1);
-    major_circ.add_box(circbox, {0});
+    unit_vector_t new_args;
+    new_args.push_back(Bit(0));
+    new_args.push_back(WasmState(0));
+    new_args.push_back(WasmState(1));
+    new_args.push_back(WasmState(2));
+    major_circ.add_op(std::make_shared<CircBox>(circbox), new_args);
 
     REQUIRE(major_circ.depth() == 1);
     REQUIRE(major_circ.get_wasm_file_uid() == wasm_file);