diff --git a/api/src/main/java/org/apache/iceberg/Schema.java b/api/src/main/java/org/apache/iceberg/Schema.java
index 3e59998be476..ed4d1d60e901 100644
--- a/api/src/main/java/org/apache/iceberg/Schema.java
+++ b/api/src/main/java/org/apache/iceberg/Schema.java
@@ -81,6 +81,7 @@ public class Schema implements Serializable {
   private transient Map<Integer, Accessor<StructLike>> idToAccessor = null;
   private transient Map<Integer, String> idToName = null;
   private transient Set<Integer> identifierFieldIdSet = null;
+  private transient Set<String> identifierFieldNameSet = null;
   private final transient Map<Integer, Integer> idsToReassigned;
   private final transient Map<Integer, Integer> idsToOriginal;
 
@@ -254,6 +255,16 @@ private Set<Integer> lazyIdentifierFieldIdSet() {
     return identifierFieldIdSet;
   }
 
+  private Set<String> lazyIdentifierFieldNameSet() {
+    if (identifierFieldNameSet == null) {
+      this.identifierFieldNameSet =
+          lazyIdentifierFieldIdSet().stream()
+              .map(id -> lazyIdToName().get(id))
+              .collect(ImmutableSet.toImmutableSet());
+    }
+    return identifierFieldNameSet;
+  }
+
   /**
    * Returns the schema ID for this schema.
    *
@@ -331,9 +342,7 @@ public Set<Integer> identifierFieldIds() {
 
   /** Returns the set of identifier field names. */
   public Set<String> identifierFieldNames() {
-    return identifierFieldIds().stream()
-        .map(id -> lazyIdToName().get(id))
-        .collect(Collectors.toSet());
+    return lazyIdentifierFieldNameSet();
   }
 
   /**
diff --git a/core/src/main/java/org/apache/iceberg/SchemaUpdate.java b/core/src/main/java/org/apache/iceberg/SchemaUpdate.java
index 1fa6ebbe8fef..ed26bdb82446 100644
--- a/core/src/main/java/org/apache/iceberg/SchemaUpdate.java
+++ b/core/src/main/java/org/apache/iceberg/SchemaUpdate.java
@@ -87,7 +87,7 @@ private SchemaUpdate(TableOperations ops, TableMetadata base, Schema schema, int
     this.schema = schema;
     this.lastColumnId = lastColumnId;
     this.idToParent = Maps.newHashMap(TypeUtil.indexParents(schema.asStruct()));
-    this.identifierFieldNames = schema.identifierFieldNames();
+    this.identifierFieldNames = Sets.newHashSet(schema.identifierFieldNames());
   }
 
   @Override