diff --git a/src/kyupy/circuit.py b/src/kyupy/circuit.py
index aaad109..e387ffc 100644
--- a/src/kyupy/circuit.py
+++ b/src/kyupy/circuit.py
@@ -312,7 +312,7 @@ class Circuit:
     def _locs(self, prefix, nodes):
         d_top = dict()
         for i, n in enumerate(nodes):
-            if m := re.match(fr'({prefix}.*?)((?:[\d_\[\]])*$)', n.name):
+            if m := re.match(fr'({re.escape(prefix)}.*?)((?:[\d_\[\]])*$)', n.name):
                 path = [m[1]] + [int(v) for v in re.split(r'[_\[\]]+', m[2]) if len(v) > 0]
                 d = d_top
                 for j in path[:-1]:
diff --git a/src/kyupy/sdf.py b/src/kyupy/sdf.py
index 32ff2be..5314efb 100644
--- a/src/kyupy/sdf.py
+++ b/src/kyupy/sdf.py
@@ -107,8 +107,8 @@ class DelayFile:
         for n1, n2, *delvals in self._interconnects:
             delvals = [d if len(d) > 0 else [0, 0, 0] for d in delvals]
             if max(max(delvals)) == 0: continue
-            cn1, pn1 = n1.split('/') if '/' in n1 else (n1, None)
-            cn2, pn2 = n2.split('/') if '/' in n2 else (n2, None)
+            cn1, pn1 = (n1, None) if (slash := n1.rfind('/')) < 0 else (n1[:slash], n1[slash+1:])
+            cn2, pn2 = (n2, None) if (slash := n2.rfind('/')) < 0 else (n2[:slash], n2[slash+1:])
             cn1 = cn1.replace('\\','')
             cn2 = cn2.replace('\\','')
             c1, c2 = circuit.cells[cn1], circuit.cells[cn2]
diff --git a/src/kyupy/verilog.py b/src/kyupy/verilog.py
index 1c6a0d1..0938a81 100644
--- a/src/kyupy/verilog.py
+++ b/src/kyupy/verilog.py
@@ -123,6 +123,9 @@ class VerilogTransformer(Transformer):
         assignments = []
         for stmt in args[2:]:  # pass 1: instantiate cells and driven signals
             if isinstance(stmt, Instantiation):
+                if stmt.type not in self.tlib.cells:
+                    log.warn(f'Ignoring cell of unknown kind "{stmt.type}"')
+                    continue
                 n = Node(c, stmt.name, kind=stmt.type)
                 for p, s in stmt.pins.items():
                     if self.tlib.pin_is_output(n.kind, p):
@@ -141,35 +144,41 @@ class VerilogTransformer(Transformer):
                         c.io_nodes[positions[name]] = n
                     if sd.kind == 'input':
                         Line(c, n, Node(c, name))
-        for target, source in assignments:  # pass 1.5: process signal assignments
-            target_sigs = []
-            if not isinstance(target, list): target = [target]
-            for s in target:
-                if s in sig_decls:
-                    target_sigs += sig_decls[s].names
-                else:
-                    target_sigs.append(s)
-            source_sigs = []
-            if not isinstance(source, list): source = [source]
-            for s in source:
-                if s in sig_decls:
-                    source_sigs += sig_decls[s].names
-                else:
-                    source_sigs.append(s)
-            for t, s in zip(target_sigs, source_sigs):
-                if t in c.forks:
-                    assert s not in c.forks, 'assignment between two driven signals'
-                    Line(c, c.forks[t], Node(c, s))
-                elif s in c.forks:
-                    assert t not in c.forks, 'assignment between two driven signals'
-                    Line(c, c.forks[s], Node(c, t))
-                elif s.startswith("1'b"):
-                    cnode = Node(c, f'__const{s[3]}_{const_count}__', f'__const{s[3]}__')
-                    const_count += 1
-                    Line(c, cnode, Node(c, t))
+        while len(assignments) > 0:
+            more_assignments = []
+            for target, source in assignments:  # pass 1.5: process signal assignments
+                target_sigs = []
+                if not isinstance(target, list): target = [target]
+                for s in target:
+                    if s in sig_decls:
+                        target_sigs += sig_decls[s].names
+                    else:
+                        target_sigs.append(s)
+                source_sigs = []
+                if not isinstance(source, list): source = [source]
+                for s in source:
+                    if s in sig_decls:
+                        source_sigs += sig_decls[s].names
+                    else:
+                        source_sigs.append(s)
+                for t, s in zip(target_sigs, source_sigs):
+                    if t in c.forks:
+                        assert s not in c.forks, 'assignment between two driven signals'
+                        Line(c, c.forks[t], Node(c, s))
+                    elif s in c.forks:
+                        assert t not in c.forks, 'assignment between two driven signals'
+                        Line(c, c.forks[s], Node(c, t))
+                    elif s.startswith("1'b"):
+                        cnode = Node(c, f'__const{s[3]}_{const_count}__', f'__const{s[3]}__')
+                        const_count += 1
+                        Line(c, cnode, Node(c, t))
+                    else:
+                        more_assignments.append((target, source))
+            assignments = more_assignments
         for stmt in args[2:]:  # pass 2: connect signals to readers
             if isinstance(stmt, Instantiation):
                 for p, s in stmt.pins.items():
+                    if stmt.name not in c.cells: continue
                     n = c.cells[stmt.name]
                     if self.tlib.pin_is_output(n.kind, p): continue
                     if s.startswith("1'b"):