09a40b
@@ -223,7 +223,8 @@
public class InvocableHandlerMethod extends HandlerMethod {
 		}
 		catch (IllegalArgumentException ex) {
 			assertTargetBean(getBridgedMethod(), getBean(), args);
-			throw new IllegalStateException(getInvocationErrorMessage(ex.getMessage(), args), ex);
+			String message = (ex.getMessage() != null ? ex.getMessage() : "Illegal argument");
+			throw new IllegalStateException(getInvocationErrorMessage(message, args), ex);
 		}
 		catch (InvocationTargetException ex) {
 			// Unwrap for HandlerExceptionResolvers ...
