diff --git a/models/spring-ai-openai/src/main/java/org/springframework/ai/openai/api/OpenAiApi.java b/models/spring-ai-openai/src/main/java/org/springframework/ai/openai/api/OpenAiApi.java
index 21a90a5d848..383065fc209 100644
--- a/models/spring-ai-openai/src/main/java/org/springframework/ai/openai/api/OpenAiApi.java
+++ b/models/spring-ai-openai/src/main/java/org/springframework/ai/openai/api/OpenAiApi.java
@@ -1909,7 +1909,6 @@ public Builder apiKey(ApiKey apiKey) {
 		}
 
 		public Builder apiKey(String simpleApiKey) {
-			Assert.notNull(simpleApiKey, "simpleApiKey cannot be null");
 			this.apiKey = new SimpleApiKey(simpleApiKey);
 			return this;
 		}