diff --git a/mcp-core/src/main/java/io/modelcontextprotocol/spec/HttpHeaders.java b/mcp-core/src/main/java/io/modelcontextprotocol/spec/HttpHeaders.java
index 65b80957c..370b47070 100644
--- a/mcp-core/src/main/java/io/modelcontextprotocol/spec/HttpHeaders.java
+++ b/mcp-core/src/main/java/io/modelcontextprotocol/spec/HttpHeaders.java
@@ -14,7 +14,7 @@ public interface HttpHeaders {
 	/**
 	 * Identifies individual MCP sessions.
 	 */
-	String MCP_SESSION_ID = "mcp-session-id";
+	String MCP_SESSION_ID = "Mcp-Session-Id";
 
 	/**
 	 * Identifies events within an SSE Stream.