diff --git a/checker/src/main/java/org/checkerframework/checker/fenum/FenumVisitor.java b/checker/src/main/java/org/checkerframework/checker/fenum/FenumVisitor.java
index 96f729f322a..0a7580c77f3 100644
--- a/checker/src/main/java/org/checkerframework/checker/fenum/FenumVisitor.java
+++ b/checker/src/main/java/org/checkerframework/checker/fenum/FenumVisitor.java
@@ -15,7 +15,7 @@
 import org.checkerframework.framework.type.AnnotatedTypeMirror.AnnotatedExecutableType;
 import org.checkerframework.javacutil.AnnotationMirrorSet;
 import org.checkerframework.javacutil.TreeUtils;
-import org.checkerframework.javacutil.trees.TreeUtilsAfterJava11.CaseUtils;
+import org.checkerframework.javacutil.TreeUtilsAfterJava11.CaseUtils;
 
 /** The visitor for Fenum Checker. */
 public class FenumVisitor extends BaseTypeVisitor<FenumAnnotatedTypeFactory> {
diff --git a/checker/tests/nullness/java21/FlowSwitch.java b/checker/tests/nullness/java21/FlowSwitch.java
index 4d9d091a6a1..e103357346f 100644
--- a/checker/tests/nullness/java21/FlowSwitch.java
+++ b/checker/tests/nullness/java21/FlowSwitch.java
@@ -7,6 +7,18 @@
 
 public class FlowSwitch {
 
+  void test0(Number n) {
+    String s = null;
+    switch (n) {
+      case null, default: {
+        // TODO: this should issue a dereference of nullable error.
+        n.toString();
+        s = "";
+      }
+    }
+    s.toString();
+  }
+
   void test1(Integer i) {
     String msg = null;
     switch (i) {
@@ -36,6 +48,7 @@ void test2(Integer i) {
         msg = "pos";
         break;
     }
+    msg.toString();
   }
 
   class A {}
diff --git a/dataflow/src/main/java/org/checkerframework/dataflow/cfg/builder/CFGTranslationPhaseOne.java b/dataflow/src/main/java/org/checkerframework/dataflow/cfg/builder/CFGTranslationPhaseOne.java
index 5b90e2ce6c1..fe0beceb586 100644
--- a/dataflow/src/main/java/org/checkerframework/dataflow/cfg/builder/CFGTranslationPhaseOne.java
+++ b/dataflow/src/main/java/org/checkerframework/dataflow/cfg/builder/CFGTranslationPhaseOne.java
@@ -168,16 +168,16 @@
 import org.checkerframework.javacutil.SystemUtil;
 import org.checkerframework.javacutil.TreePathUtil;
 import org.checkerframework.javacutil.TreeUtils;
+import org.checkerframework.javacutil.TreeUtilsAfterJava11.BindingPatternUtils;
+import org.checkerframework.javacutil.TreeUtilsAfterJava11.CaseUtils;
+import org.checkerframework.javacutil.TreeUtilsAfterJava11.DeconstructionPatternUtils;
+import org.checkerframework.javacutil.TreeUtilsAfterJava11.InstanceOfUtils;
+import org.checkerframework.javacutil.TreeUtilsAfterJava11.SwitchExpressionUtils;
+import org.checkerframework.javacutil.TreeUtilsAfterJava11.YieldUtils;
 import org.checkerframework.javacutil.TypeAnnotationUtils;
 import org.checkerframework.javacutil.TypeKindUtils;
 import org.checkerframework.javacutil.TypesUtils;
 import org.checkerframework.javacutil.trees.TreeBuilder;
-import org.checkerframework.javacutil.trees.TreeUtilsAfterJava11.BindingPatternUtils;
-import org.checkerframework.javacutil.trees.TreeUtilsAfterJava11.CaseUtils;
-import org.checkerframework.javacutil.trees.TreeUtilsAfterJava11.DeconstructionPatternUtils;
-import org.checkerframework.javacutil.trees.TreeUtilsAfterJava11.InstanceOfUtils;
-import org.checkerframework.javacutil.trees.TreeUtilsAfterJava11.SwitchExpressionUtils;
-import org.checkerframework.javacutil.trees.TreeUtilsAfterJava11.YieldUtils;
 import org.plumelib.util.ArrayMap;
 import org.plumelib.util.ArraySet;
 import org.plumelib.util.CollectionsPlume;
diff --git a/framework/src/main/java/org/checkerframework/common/basetype/BaseTypeVisitor.java b/framework/src/main/java/org/checkerframework/common/basetype/BaseTypeVisitor.java
index fc060c02be7..6f900e062d1 100644
--- a/framework/src/main/java/org/checkerframework/common/basetype/BaseTypeVisitor.java
+++ b/framework/src/main/java/org/checkerframework/common/basetype/BaseTypeVisitor.java
@@ -141,9 +141,9 @@
 import org.checkerframework.javacutil.TreePathUtil;
 import org.checkerframework.javacutil.TreeUtils;
 import org.checkerframework.javacutil.TreeUtils.MemberReferenceKind;
+import org.checkerframework.javacutil.TreeUtilsAfterJava11.BindingPatternUtils;
+import org.checkerframework.javacutil.TreeUtilsAfterJava11.InstanceOfUtils;
 import org.checkerframework.javacutil.TypesUtils;
-import org.checkerframework.javacutil.trees.TreeUtilsAfterJava11.BindingPatternUtils;
-import org.checkerframework.javacutil.trees.TreeUtilsAfterJava11.InstanceOfUtils;
 import org.plumelib.util.ArrayMap;
 import org.plumelib.util.ArraySet;
 import org.plumelib.util.ArraysPlume;
diff --git a/framework/src/main/java/org/checkerframework/framework/ajava/ExpectedTreesVisitor.java b/framework/src/main/java/org/checkerframework/framework/ajava/ExpectedTreesVisitor.java
index f7dfa2d2cf0..c4cd4ec3cca 100644
--- a/framework/src/main/java/org/checkerframework/framework/ajava/ExpectedTreesVisitor.java
+++ b/framework/src/main/java/org/checkerframework/framework/ajava/ExpectedTreesVisitor.java
@@ -26,8 +26,8 @@
 import java.util.HashSet;
 import java.util.Set;
 import org.checkerframework.javacutil.TreeUtils;
-import org.checkerframework.javacutil.trees.TreeUtilsAfterJava11.BindingPatternUtils;
-import org.checkerframework.javacutil.trees.TreeUtilsAfterJava11.SwitchExpressionUtils;
+import org.checkerframework.javacutil.TreeUtilsAfterJava11.BindingPatternUtils;
+import org.checkerframework.javacutil.TreeUtilsAfterJava11.SwitchExpressionUtils;
 
 /**
  * After this visitor visits a tree, {@link #getTrees} returns all the trees that should match with
diff --git a/framework/src/main/java/org/checkerframework/framework/ajava/JointJavacJavaParserVisitor.java b/framework/src/main/java/org/checkerframework/framework/ajava/JointJavacJavaParserVisitor.java
index 8e0299ad7fb..2882e95f8c1 100644
--- a/framework/src/main/java/org/checkerframework/framework/ajava/JointJavacJavaParserVisitor.java
+++ b/framework/src/main/java/org/checkerframework/framework/ajava/JointJavacJavaParserVisitor.java
@@ -161,11 +161,11 @@
 import org.checkerframework.checker.nullness.qual.Nullable;
 import org.checkerframework.javacutil.BugInCF;
 import org.checkerframework.javacutil.TreeUtils;
-import org.checkerframework.javacutil.trees.TreeUtilsAfterJava11.BindingPatternUtils;
-import org.checkerframework.javacutil.trees.TreeUtilsAfterJava11.CaseUtils;
-import org.checkerframework.javacutil.trees.TreeUtilsAfterJava11.InstanceOfUtils;
-import org.checkerframework.javacutil.trees.TreeUtilsAfterJava11.SwitchExpressionUtils;
-import org.checkerframework.javacutil.trees.TreeUtilsAfterJava11.YieldUtils;
+import org.checkerframework.javacutil.TreeUtilsAfterJava11.BindingPatternUtils;
+import org.checkerframework.javacutil.TreeUtilsAfterJava11.CaseUtils;
+import org.checkerframework.javacutil.TreeUtilsAfterJava11.InstanceOfUtils;
+import org.checkerframework.javacutil.TreeUtilsAfterJava11.SwitchExpressionUtils;
+import org.checkerframework.javacutil.TreeUtilsAfterJava11.YieldUtils;
 
 /**
  * A visitor that processes javac trees and JavaParser nodes simultaneously, matching corresponding
diff --git a/javacutil/src/main/java/org/checkerframework/javacutil/SwitchExpressionScanner.java b/javacutil/src/main/java/org/checkerframework/javacutil/SwitchExpressionScanner.java
index eb82e041898..1ae0cd41f57 100644
--- a/javacutil/src/main/java/org/checkerframework/javacutil/SwitchExpressionScanner.java
+++ b/javacutil/src/main/java/org/checkerframework/javacutil/SwitchExpressionScanner.java
@@ -9,9 +9,9 @@
 import java.util.function.BiFunction;
 import org.checkerframework.checker.nullness.qual.NonNull;
 import org.checkerframework.checker.nullness.qual.Nullable;
-import org.checkerframework.javacutil.trees.TreeUtilsAfterJava11.CaseUtils;
-import org.checkerframework.javacutil.trees.TreeUtilsAfterJava11.SwitchExpressionUtils;
-import org.checkerframework.javacutil.trees.TreeUtilsAfterJava11.YieldUtils;
+import org.checkerframework.javacutil.TreeUtilsAfterJava11.CaseUtils;
+import org.checkerframework.javacutil.TreeUtilsAfterJava11.SwitchExpressionUtils;
+import org.checkerframework.javacutil.TreeUtilsAfterJava11.YieldUtils;
 
 /**
  * A class that visits each result expression of a switch expression and calls {@link
diff --git a/javacutil/src/main/java/org/checkerframework/javacutil/TreeUtils.java b/javacutil/src/main/java/org/checkerframework/javacutil/TreeUtils.java
index a1fbdd1d565..d0f3cfbe6cb 100644
--- a/javacutil/src/main/java/org/checkerframework/javacutil/TreeUtils.java
+++ b/javacutil/src/main/java/org/checkerframework/javacutil/TreeUtils.java
@@ -88,11 +88,11 @@
 import org.checkerframework.checker.nullness.qual.Nullable;
 import org.checkerframework.checker.signature.qual.FullyQualifiedName;
 import org.checkerframework.dataflow.qual.Pure;
-import org.checkerframework.javacutil.trees.TreeUtilsAfterJava11.BindingPatternUtils;
-import org.checkerframework.javacutil.trees.TreeUtilsAfterJava11.CaseUtils;
-import org.checkerframework.javacutil.trees.TreeUtilsAfterJava11.InstanceOfUtils;
-import org.checkerframework.javacutil.trees.TreeUtilsAfterJava11.SwitchExpressionUtils;
-import org.checkerframework.javacutil.trees.TreeUtilsAfterJava11.YieldUtils;
+import org.checkerframework.javacutil.TreeUtilsAfterJava11.BindingPatternUtils;
+import org.checkerframework.javacutil.TreeUtilsAfterJava11.CaseUtils;
+import org.checkerframework.javacutil.TreeUtilsAfterJava11.InstanceOfUtils;
+import org.checkerframework.javacutil.TreeUtilsAfterJava11.SwitchExpressionUtils;
+import org.checkerframework.javacutil.TreeUtilsAfterJava11.YieldUtils;
 import org.plumelib.util.CollectionsPlume;
 import org.plumelib.util.UniqueIdMap;
 
@@ -2220,13 +2220,14 @@ public static boolean sameTree(ExpressionTree expr1, ExpressionTree expr2) {
   }
 
   /**
-   * Returns true if this is the default case for a switch statement or expression.
+   * Returns true if this is the default case for a switch statement or expression. (Also, returns
+   * true if {@code caseTree} is {@code case null, default:}.)
    *
    * @param caseTree a case tree
    * @return true if {@code caseTree} is the default case for a switch statement or expression
    */
   public static boolean isDefaultCaseTree(CaseTree caseTree) {
-    return CaseUtils.getLabels(caseTree).isEmpty();
+    return CaseUtils.isDefaultCaseTree(caseTree);
   }
 
   /**
diff --git a/javacutil/src/main/java/org/checkerframework/javacutil/trees/TreeUtilsAfterJava11.java b/javacutil/src/main/java/org/checkerframework/javacutil/TreeUtilsAfterJava11.java
similarity index 93%
rename from javacutil/src/main/java/org/checkerframework/javacutil/trees/TreeUtilsAfterJava11.java
rename to javacutil/src/main/java/org/checkerframework/javacutil/TreeUtilsAfterJava11.java
index 73d5f70333b..54cc6b10b5e 100644
--- a/javacutil/src/main/java/org/checkerframework/javacutil/trees/TreeUtilsAfterJava11.java
+++ b/javacutil/src/main/java/org/checkerframework/javacutil/TreeUtilsAfterJava11.java
@@ -1,4 +1,4 @@
-package org.checkerframework.javacutil.trees;
+package org.checkerframework.javacutil;
 
 import com.sun.source.tree.CaseTree;
 import com.sun.source.tree.ExpressionTree;
@@ -13,8 +13,6 @@
 import javax.lang.model.SourceVersion;
 import org.checkerframework.checker.nullness.qual.Nullable;
 import org.checkerframework.checker.signature.qual.ClassGetName;
-import org.checkerframework.javacutil.BugInCF;
-import org.checkerframework.javacutil.TreeUtils;
 
 /**
  * This class contains util methods for reflective accessing Tree classes and methods that were
@@ -116,14 +114,39 @@ public static boolean isCaseRule(CaseTree caseTree) {
     }
 
     /**
-     * Get the list of labels from a case expression. For {@code default}, this is empty. Otherwise,
-     * in JDK 11 and earlier, this is a singleton list of expression trees. In JDK 12, this is a
-     * list of expression trees. In JDK 21+, this is a list of expression and pattern trees.
+     * Get the list of labels from a case expression. For {@code default}, this is empty. For {@code
+     * case null, default}, the list contains {@code null}. Otherwise, in JDK 11 and earlier, this
+     * is a list of a single expression tree. In JDK 12+, the list may have multiple expression
+     * trees. In JDK 21+, the list might contain a single pattern tree.
      *
      * @param caseTree the case expression to get the labels from
      * @return the list of case labels in the case
      */
     public static List<? extends Tree> getLabels(CaseTree caseTree) {
+      return getLabels(caseTree, false);
+    }
+
+    /**
+     * Returns true if this is the default case for a switch statement or expression. (Also, returns
+     * true if {@code caseTree} is {@code case null, default:}.)
+     *
+     * @param caseTree a case tree
+     * @return true if {@code caseTree} is the default case for a switch statement or expression
+     */
+    public static boolean isDefaultCaseTree(CaseTree caseTree) {
+      if (sourceVersionNumber >= 21) {
+        for (Tree label : getLabels(caseTree, true)) {
+          if (TreeUtils.isDefaultCaseLabelTree(label)) {
+            return true;
+          }
+        }
+        return false;
+      } else {
+        return getExpressions(caseTree).isEmpty();
+      }
+    }
+
+    private static List<? extends Tree> getLabels(CaseTree caseTree, boolean useDefault) {
       if (sourceVersionNumber >= 21) {
         if (GET_LABELS == null) {
           GET_LABELS = getMethod(CaseTree.class, "getLabels");
@@ -134,7 +157,9 @@ public static List<? extends Tree> getLabels(CaseTree caseTree) {
         List<Tree> labels = new ArrayList<>();
         for (Tree caseLabel : caseLabelTrees) {
           if (TreeUtils.isDefaultCaseLabelTree(caseLabel)) {
-            return Collections.emptyList();
+            if (useDefault) {
+              labels.add(caseLabel);
+            }
           } else if (TreeUtils.isConstantCaseLabelTree(caseLabel)) {
             labels.add(ConstantCaseLabelUtils.getConstantExpression(caseLabel));
           } else if (TreeUtils.isPatternCaseLabelTree(caseLabel)) {
@@ -184,7 +209,7 @@ public static List<? extends ExpressionTree> getExpressions(CaseTree caseTree) {
       if (GET_GUARD == null) {
         GET_GUARD = getMethod(CaseTree.class, "getGuard");
       }
-      return (ExpressionTree) invokeNonNullResult(GET_GUARD, caseTree);
+      return (ExpressionTree) invoke(GET_GUARD, caseTree);
     }
   }