diff --git a/core/src/main/java/io/substrait/extension/DefaultExtensionCatalog.java b/core/src/main/java/io/substrait/extension/DefaultExtensionCatalog.java
index 25dc76cad..6f5ecc852 100644
--- a/core/src/main/java/io/substrait/extension/DefaultExtensionCatalog.java
+++ b/core/src/main/java/io/substrait/extension/DefaultExtensionCatalog.java
@@ -63,6 +63,9 @@ public class DefaultExtensionCatalog {
   /** Identifier for extension types. */
   public static final String EXTENSION_TYPES = "extension:io.substrait:extension_types";
 
+  /** Extension identifier for unsigned integer types and functions. */
+  public static final String UNSIGNED_INTEGERS = "extension:io.substrait:unsigned_integers";
+
   /** Default collection of built-in extensions loaded from YAML resources. */
   public static final SimpleExtension.ExtensionCollection DEFAULT_COLLECTION =
       loadDefaultCollection();
@@ -93,6 +96,7 @@ private static SimpleExtension.ExtensionCollection loadDefaultCollection() {
             .collect(Collectors.toList());
 
     defaultFiles.add("/substrait/extensions/extension_types.yaml");
+    defaultFiles.add("/substrait/extensions/unsigned_integers.yaml");
 
     return SimpleExtension.load(defaultFiles);
   }
diff --git a/core/src/main/java/io/substrait/relation/Expand.java b/core/src/main/java/io/substrait/relation/Expand.java
index 33af9033b..4573493e5 100644
--- a/core/src/main/java/io/substrait/relation/Expand.java
+++ b/core/src/main/java/io/substrait/relation/Expand.java
@@ -13,7 +13,7 @@
  */
 @Value.Enclosing
 @Value.Immutable
-public abstract class Expand extends SingleInputRel {
+public abstract class Expand extends SingleInputRel implements HasExtension {
 
   /**
    * Returns the fields produced by the expand operation.
diff --git a/core/src/main/java/io/substrait/relation/ProtoRelConverter.java b/core/src/main/java/io/substrait/relation/ProtoRelConverter.java
index ed7f08e2c..55b0e326f 100644
--- a/core/src/main/java/io/substrait/relation/ProtoRelConverter.java
+++ b/core/src/main/java/io/substrait/relation/ProtoRelConverter.java
@@ -962,6 +962,9 @@ protected Expand newExpand(ExpandRel rel) {
         .remap(optionalRelmap(rel.getCommon()))
         .hint(optionalHint(rel.getCommon()))
         .relAnchor(optionalRelAnchor(rel.getCommon()));
+    if (rel.hasAdvancedExtension()) {
+      builder.extension(protoExtensionConverter.fromProto(rel.getAdvancedExtension()));
+    }
     return builder.build();
   }
 
diff --git a/core/src/main/java/io/substrait/relation/RelProtoConverter.java b/core/src/main/java/io/substrait/relation/RelProtoConverter.java
index 0096a872f..7333d22dc 100644
--- a/core/src/main/java/io/substrait/relation/RelProtoConverter.java
+++ b/core/src/main/java/io/substrait/relation/RelProtoConverter.java
@@ -814,6 +814,10 @@ public Rel visit(Expand expand, EmptyVisitationContext context) throws RuntimeEx
                     "Consistent or Switching fields must be set for the Expand relation.");
               }
             });
+
+    expand
+        .getExtension()
+        .ifPresent(ae -> builder.setAdvancedExtension(extensionProtoConverter.toProto(ae)));
     return Rel.newBuilder().setExpand(builder).build();
   }
 
diff --git a/core/src/test/java/io/substrait/type/proto/ExtensionRoundtripTest.java b/core/src/test/java/io/substrait/type/proto/ExtensionRoundtripTest.java
index 048c393e0..8b2c31dd9 100644
--- a/core/src/test/java/io/substrait/type/proto/ExtensionRoundtripTest.java
+++ b/core/src/test/java/io/substrait/type/proto/ExtensionRoundtripTest.java
@@ -260,6 +260,7 @@ void expand() {
         Expand.builder()
             .from(sb.expand(__ -> Collections.emptyList(), commonTable))
             .commonExtension(commonExtension)
+            .extension(relExtension)
             .build();
     verifyRoundTrip(rel);
   }
diff --git a/gradle/libs.versions.toml b/gradle/libs.versions.toml
index 7de44faba..ee6b87548 100644
--- a/gradle/libs.versions.toml
+++ b/gradle/libs.versions.toml
@@ -29,7 +29,7 @@ spark-3-5 = "3.5.4"
 spark-4-0 = "4.0.2"
 spotless = "8.9.0"
 # substrait-packaging artifacts, versioned by the Substrait spec release they are generated from.
-substrait-packaging = "0.99.0"
+substrait-packaging = "0.100.0"
 testcontainers = "2.0.5"
 validator = "3.0.6"