diff --git a/core/src/main/java/io/substrait/expression/Expression.java b/core/src/main/java/io/substrait/expression/Expression.java
index 9fc719f35..aa9e69148 100644
--- a/core/src/main/java/io/substrait/expression/Expression.java
+++ b/core/src/main/java/io/substrait/expression/Expression.java
@@ -940,6 +940,7 @@ public static AggregationInvocation fromProto(AggregateFunction.AggregationInvoc
   }
 
   enum AggregationPhase {
+    UNSPECIFIED(io.substrait.proto.AggregationPhase.AGGREGATION_PHASE_UNSPECIFIED),
     INITIAL_TO_INTERMEDIATE(
         io.substrait.proto.AggregationPhase.AGGREGATION_PHASE_INITIAL_TO_INTERMEDIATE),
     INTERMEDIATE_TO_INTERMEDIATE(