diff --git a/core/src/main/java/com/google/adk/events/EventActions.java b/core/src/main/java/com/google/adk/events/EventActions.java
index 1ca856b45..3565c3e99 100644
--- a/core/src/main/java/com/google/adk/events/EventActions.java
+++ b/core/src/main/java/com/google/adk/events/EventActions.java
@@ -287,8 +287,14 @@ public Builder skipSummarization(boolean skipSummarization) {
 
     @CanIgnoreReturnValue
     @JsonProperty("stateDelta")
-    public Builder stateDelta(ConcurrentMap<String, Object> value) {
-      this.stateDelta = value;
+    public Builder stateDelta(@Nullable Map<String, Object> value) {
+      if (value == null) {
+        this.stateDelta = new ConcurrentHashMap<>();
+      } else if (value instanceof ConcurrentMap) {
+        this.stateDelta = (ConcurrentMap<String, Object>) value;
+      } else {
+        this.stateDelta = new ConcurrentHashMap<>(value);
+      }
       return this;
     }