diff --git a/protobuf/src/main/java/dev/cel/protobuf/CelLiteDescriptor.java b/protobuf/src/main/java/dev/cel/protobuf/CelLiteDescriptor.java
index 305da6bc7..e2b299445 100644
--- a/protobuf/src/main/java/dev/cel/protobuf/CelLiteDescriptor.java
+++ b/protobuf/src/main/java/dev/cel/protobuf/CelLiteDescriptor.java
@@ -397,6 +397,27 @@ public FieldLiteDescriptor(
     return defaultScalarValues.contains(value) ? null : value;
   }
 
+  /** Describes map entry type {@code fullName}, whose key and value are fields 1 and 2. */
+  protected static MessageLiteDescriptor mapEntry(
+      String fullName,
+      FieldLiteDescriptor.Type keyType,
+      FieldLiteDescriptor.Type valueType,
+      String valueTypeName) {
+    return new MessageLiteDescriptor(
+        fullName,
+        Arrays.asList(
+            new FieldLiteDescriptor(
+                1, "key", FieldLiteDescriptor.EncodingType.SINGULAR, keyType, false, ""),
+            new FieldLiteDescriptor(
+                2,
+                "value",
+                FieldLiteDescriptor.EncodingType.SINGULAR,
+                valueType,
+                false,
+                valueTypeName)),
+        () -> null);
+  }
+
   protected CelLiteDescriptor(String version, List<MessageLiteDescriptor> messageInfoList) {
     Map<String, MessageLiteDescriptor> protoFqnMap =
         new HashMap<>(getMapInitialCapacity(messageInfoList.size()));
diff --git a/protobuf/src/main/java/dev/cel/protobuf/templates/cel_lite_descriptor_template.txt b/protobuf/src/main/java/dev/cel/protobuf/templates/cel_lite_descriptor_template.txt
index 512b0564d..35d7b8401 100644
--- a/protobuf/src/main/java/dev/cel/protobuf/templates/cel_lite_descriptor_template.txt
+++ b/protobuf/src/main/java/dev/cel/protobuf/templates/cel_lite_descriptor_template.txt
@@ -40,6 +40,7 @@ public final class ${descriptor_class_name} extends CelLiteDescriptor {
     List<MessageLiteDescriptor> descriptors = new ArrayList<>(${descriptor_metadata_list?size});
     List<FieldLiteDescriptor> fieldDescriptors;
     <#list descriptor_metadata_list as descriptor_metadata>
+    <#if descriptor_metadata.javaClassName??>
 
     fieldDescriptors = new ArrayList<>(${descriptor_metadata.fieldDescriptors?size});
       <#list descriptor_metadata.fieldDescriptors as field_descriptor>
@@ -57,13 +58,17 @@ public final class ${descriptor_class_name} extends CelLiteDescriptor {
       new MessageLiteDescriptor(
         "${descriptor_metadata.protoTypeName}",
         fieldDescriptors,
-        <#if descriptor_metadata.javaClassName??>
         ${descriptor_metadata.javaClassName}::newBuilder
-        <#else>
-        () -> null
-        </#if>
         )
     );
+    <#else>
+
+    descriptors.add(mapEntry(
+      "${descriptor_metadata.protoTypeName}",
+      ${descriptor_metadata.fieldDescriptors[0].protoFieldTypeEnumName},
+      ${descriptor_metadata.fieldDescriptors[1].protoFieldTypeEnumName},
+      "${descriptor_metadata.fieldDescriptors[1].fieldProtoTypeName}"));
+    </#if>
     </#list>
 
     return Collections.unmodifiableList(descriptors);
diff --git a/protobuf/src/test/java/dev/cel/protobuf/CelLiteDescriptorTest.java b/protobuf/src/test/java/dev/cel/protobuf/CelLiteDescriptorTest.java
index 98434273d..1eb53da65 100644
--- a/protobuf/src/test/java/dev/cel/protobuf/CelLiteDescriptorTest.java
+++ b/protobuf/src/test/java/dev/cel/protobuf/CelLiteDescriptorTest.java
@@ -178,6 +178,30 @@ public void fieldDescriptor_nestedMessage_fullyQualifiedNames() {
         .isEqualTo("cel.expr.conformance.proto3.TestAllTypes.NestedMessage");
   }
 
+  @Test
+  public void mapEntryDescriptor_describesKeyAndValue() {
+    MessageLiteDescriptor mapEntryDescriptor =
+        TEST_ALL_TYPES_CEL_LITE_DESCRIPTOR
+            .getProtoTypeNamesToDescriptors()
+            .get("cel.expr.conformance.proto3.TestAllTypes.MapInt64NestedTypeEntry");
+
+    FieldLiteDescriptor key = mapEntryDescriptor.getByFieldNumberOrThrow(1);
+    FieldLiteDescriptor value = mapEntryDescriptor.getByFieldNumberOrThrow(2);
+
+    assertThat(mapEntryDescriptor.newMessageBuilder()).isNull();
+    assertThat(key.getFieldName()).isEqualTo("key");
+    assertThat(key.getEncodingType()).isEqualTo(EncodingType.SINGULAR);
+    assertThat(key.getProtoFieldType()).isEqualTo(FieldLiteDescriptor.Type.INT64);
+    assertThat(key.getIsPacked()).isFalse();
+    assertThat(key.getFieldProtoTypeName()).isEmpty();
+    assertThat(value.getFieldName()).isEqualTo("value");
+    assertThat(value.getEncodingType()).isEqualTo(EncodingType.SINGULAR);
+    assertThat(value.getProtoFieldType()).isEqualTo(FieldLiteDescriptor.Type.MESSAGE);
+    assertThat(value.getIsPacked()).isFalse();
+    assertThat(value.getFieldProtoTypeName())
+        .isEqualTo("cel.expr.conformance.proto3.NestedTestAllTypes");
+  }
+
   private enum ProtoFieldTypeTestCase {
     DOUBLE(FieldLiteDescriptor.Type.DOUBLE, 1, WireFormat.FieldType.DOUBLE),
     FLOAT(FieldLiteDescriptor.Type.FLOAT, 2, WireFormat.FieldType.FLOAT),