diff --git a/python/ql/lib/semmle/python/controlflow/internal/AstNodeImpl.qll b/python/ql/lib/semmle/python/controlflow/internal/AstNodeImpl.qll
index 8a6c7cf81c52..1747b6cdd1a0 100644
--- a/python/ql/lib/semmle/python/controlflow/internal/AstNodeImpl.qll
+++ b/python/ql/lib/semmle/python/controlflow/internal/AstNodeImpl.qll
@@ -993,9 +993,8 @@ module Ast implements AstSig<Py::Location> {
     }
   }
 
-  /** A wildcard case (`case _:`). */
   class DefaultCase extends Case {
-    DefaultCase() { this.isWildcard() }
+    DefaultCase() { none() }
   }
 
   /** A conditional expression (`x if cond else y`). */
@@ -1754,6 +1753,11 @@ private module Input implements InputSig1, InputSig2 {
       n2.isAdditional(assertStmt, assertThrowTag())
     )
   }
+
+  predicate matchAll(Ast::Case c) {
+    // A wildcard case (`case _:`) will match all values.
+    c.isWildcard()
+  }
 }
 
 import Public