diff --git a/compiler/src/dotty/tools/dotc/core/classfile/ClassfileConstants.scala b/compiler/src/dotty/tools/dotc/core/classfile/ClassfileConstants.scala
index 6ad71c5fd1ce..7a2232891a83 100644
--- a/compiler/src/dotty/tools/dotc/core/classfile/ClassfileConstants.scala
+++ b/compiler/src/dotty/tools/dotc/core/classfile/ClassfileConstants.scala
@@ -73,7 +73,10 @@ object ClassfileConstants {
 
   inline val CONSTANT_METHODHANDLE  = 15
   inline val CONSTANT_METHODTYPE    = 16
+  inline val CONSTANT_DYNAMIC       = 17
   inline val CONSTANT_INVOKEDYNAMIC = 18
+  inline val CONSTANT_MODULE        = 19
+  inline val CONSTANT_PACKAGE       = 20
 
   // tags describing the type of a literal in attribute values
   inline val BYTE_TAG   = 'B'
diff --git a/compiler/src/dotty/tools/dotc/core/classfile/ClassfileParser.scala b/compiler/src/dotty/tools/dotc/core/classfile/ClassfileParser.scala
index 93ebcfeee62a..894d430fe54b 100644
--- a/compiler/src/dotty/tools/dotc/core/classfile/ClassfileParser.scala
+++ b/compiler/src/dotty/tools/dotc/core/classfile/ClassfileParser.scala
@@ -106,13 +106,14 @@ object ClassfileParser {
         (in.nextByte.toInt: @switch) match {
           case CONSTANT_UTF8 | CONSTANT_UNICODE =>
             in.skip(in.nextChar)
-          case CONSTANT_CLASS | CONSTANT_STRING | CONSTANT_METHODTYPE =>
+          case CONSTANT_CLASS | CONSTANT_STRING | CONSTANT_METHODTYPE
+             | CONSTANT_MODULE | CONSTANT_PACKAGE =>
             in.skip(2)
           case CONSTANT_METHODHANDLE =>
             in.skip(3)
           case CONSTANT_FIELDREF | CONSTANT_METHODREF | CONSTANT_INTFMETHODREF
              | CONSTANT_NAMEANDTYPE | CONSTANT_INTEGER | CONSTANT_FLOAT
-             | CONSTANT_INVOKEDYNAMIC =>
+             | CONSTANT_INVOKEDYNAMIC | CONSTANT_DYNAMIC =>
             in.skip(4)
           case CONSTANT_LONG | CONSTANT_DOUBLE =>
             in.skip(8)
diff --git a/compiler/test/dotty/tools/backend/jvm/ClassfileParserTest.scala b/compiler/test/dotty/tools/backend/jvm/ClassfileParserTest.scala
new file mode 100644
index 000000000000..9263103f1712
--- /dev/null
+++ b/compiler/test/dotty/tools/backend/jvm/ClassfileParserTest.scala
@@ -0,0 +1,57 @@
+package dotty.tools.backend.jvm
+
+// painful to do Java reflection stuff without this
+import scala.language.unsafeNulls
+
+import org.junit.Assert.assertEquals
+import org.junit.Test
+
+import java.lang.reflect.Member
+
+class ClassfileParserTest {
+  @Test
+  def noConstantPoolLag(): Unit = {
+    def constNames(ms: List[Member]) = ms.collect {
+      case f if f.getName.startsWith("CONSTANT_") => f.getName
+    }.sorted
+
+    val toDotc = Map(
+      "CONSTANT_INTERFACE_METHODREF" -> "CONSTANT_INTFMETHODREF",
+      "CONSTANT_INVOKE_DYNAMIC" -> "CONSTANT_INVOKEDYNAMIC",
+      "CONSTANT_METHOD_HANDLE" -> "CONSTANT_METHODHANDLE",
+      "CONSTANT_METHOD_TYPE" -> "CONSTANT_METHODTYPE",
+      "CONSTANT_NAME_AND_TYPE" -> "CONSTANT_NAMEANDTYPE",
+    ).withDefault(x => x)
+
+    val asmConsts = constNames(Class.forName("scala.tools.asm.Symbol").getDeclaredFields.toList)
+      .map(_.stripSuffix("_TAG"))
+      .map(toDotc)
+      .::("CONSTANT_UNICODE")
+      .sorted
+    // in the Scala 2 version of this test, we also use Java reflection to get the constant
+    // names out of ClassfileConstants. in Dotty, the constants are `inline val`s, invisible
+    // to Java reflection, so we hardcode them here
+    assertEquals(asmConsts, List(
+      // do not add to this list without also making the corresponding change
+      // in ClassfileConstants! that would defeat the purpose of the test
+      "CONSTANT_CLASS",
+      "CONSTANT_DOUBLE",
+      "CONSTANT_DYNAMIC",
+      "CONSTANT_FIELDREF",
+      "CONSTANT_FLOAT",
+      "CONSTANT_INTEGER",
+      "CONSTANT_INTFMETHODREF",
+      "CONSTANT_INVOKEDYNAMIC",
+      "CONSTANT_LONG",
+      "CONSTANT_METHODHANDLE",
+      "CONSTANT_METHODREF",
+      "CONSTANT_METHODTYPE",
+      "CONSTANT_MODULE",
+      "CONSTANT_NAMEANDTYPE",
+      "CONSTANT_PACKAGE",
+      "CONSTANT_STRING",
+      "CONSTANT_UNICODE",
+      "CONSTANT_UTF8",
+    ))
+  }
+}
diff --git a/tests/pos/t12396/A_1.java b/tests/pos/t12396/A_1.java
new file mode 100644
index 000000000000..a394d3a0a59d
--- /dev/null
+++ b/tests/pos/t12396/A_1.java
@@ -0,0 +1,17 @@
+// test: -jvm 21+
+
+public class A_1 {
+  public int f(Object s) {
+    switch(s) {
+      case Res.R -> {
+        return 1;
+      }
+      default -> {
+        return 3;
+      }
+    }
+  }
+  static enum Res {
+    R
+  }
+}
diff --git a/tests/pos/t12396/B_2.scala b/tests/pos/t12396/B_2.scala
new file mode 100644
index 000000000000..662da7b3a575
--- /dev/null
+++ b/tests/pos/t12396/B_2.scala
@@ -0,0 +1,5 @@
+// test: -jvm 21+
+
+class B {
+  def bar = (new A_1).f(null)
+}