diff --git a/src/kyupy/circuit.py b/src/kyupy/circuit.py
index 228ecd4..556057c 100644
--- a/src/kyupy/circuit.py
+++ b/src/kyupy/circuit.py
@@ -448,7 +448,7 @@ class Circuit:
                     node_map[n] = Node(self, f'{node.name}~{n.name}', n.kind)
             elif len(n.outs) > 0 and len(n.ins) > 0:  # output is also read by impl. circuit, need to add a fork.
                 node_map[n] = Node(self, f'{node.name}~{n.name}')
-            elif len(n.ins) == 0 and len(n.outs) > 1:  # input is read by multiple nodes, need to add fork.
+            elif len(n.ins) == 0 and len(n.outs) != 1:  # input is read by multiple nodes (or no nodes), need to add fork.
                 node_map[n] = Node(self, f'{node.name}~{n.name}')
         for l in impl.lines:  # add all internal lines to main circuit
             if l.reader in node_map and l.driver in node_map:
diff --git a/src/kyupy/verilog.py b/src/kyupy/verilog.py
index 4aaf411..db14c32 100644
--- a/src/kyupy/verilog.py
+++ b/src/kyupy/verilog.py
@@ -52,13 +52,14 @@ class VerilogTransformer(Transformer):
     @staticmethod
     def instantiation(args):
         pinmap = {}
-        for idx, pin in enumerate(args[2:]):
-            p = pin.children[0]
-            if isinstance(p, tuple):  # named pin
-                if p[1] is not None:
-                    pinmap[p[0]] = p[1]
-            else:  # unnamed pin
-                pinmap[idx] = p
+        if args[2] is not None:
+            for idx, pin in enumerate(args[2:]):
+                p = pin.children[0]
+                if isinstance(p, tuple):  # named pin
+                    if p[1] is not None:
+                        pinmap[p[0]] = p[1]
+                else:  # unnamed pin
+                    pinmap[idx] = p
         return Instantiation(args[0], args[1], pinmap)
 
     @staticmethod