diff --git a/amaranth/tracer.py b/amaranth/tracer.py
index 3cbce9a..5a21dd0 100644
--- a/amaranth/tracer.py
+++ b/amaranth/tracer.py
@@ -24,8 +24,9 @@ def get_var_name(depth=2, default=_raise_exception):
             call_index += 2
         else:
             break
-    if call_opc not in ("CALL_FUNCTION", "CALL_FUNCTION_KW", "CALL_FUNCTION_EX", "CALL_METHOD", "CALL"):
-        return None
+    if call_opc not in ("CALL_FUNCTION", "CALL_FUNCTION_KW", "CALL_FUNCTION_EX",
+                        "CALL_METHOD", "CALL"):
+        return default
 
     index = call_index + 2
     while True: