diff --git a/core/src/main/scala/org/apache/spark/h2o/backends/external/ExternalH2OBackend.scala b/core/src/main/scala/org/apache/spark/h2o/backends/external/ExternalH2OBackend.scala
index 2e6963274d..dbfc08038e 100644
--- a/core/src/main/scala/org/apache/spark/h2o/backends/external/ExternalH2OBackend.scala
+++ b/core/src/main/scala/org/apache/spark/h2o/backends/external/ExternalH2OBackend.scala
@@ -66,7 +66,7 @@ class ExternalH2OBackend(val hc: H2OContext) extends SparklingBackend with Exter
       "-jobname", H2O_JOB_NAME.format(sparkAppId),
       "-mapperXmx", conf.mapperXmx,
       "-output", conf.HDFSOutputDir.get,
-      "-timeout", conf.clusterStartTimeout
+      "-timeout", conf.clusterStartTimeout.toString,
       "-disown"
     )