diff --git a/buildenv/jenkins/JenkinsfileBase b/buildenv/jenkins/JenkinsfileBase
index dea8db272a..377a74ddff 100644
--- a/buildenv/jenkins/JenkinsfileBase
+++ b/buildenv/jenkins/JenkinsfileBase
@@ -244,6 +244,11 @@ def setupParallelEnv() {
 					echo "Regenerate parallel list with NUM_MACHINES=${MAX_NUM_MACHINES}."
 					PARALLEL_OPTIONS = PARALLEL_OPTIONS_TEMP + " NUM_MACHINES=${MAX_NUM_MACHINES} TEST_TIME="
 					NUM_LIST = genParallelList(PARALLEL_OPTIONS)
+				} else if (NUM_LIST < 6 && env.JDK_IMPL == "openj9" && (TARGET == "extended.jck" || TARGET == "special.system")) {
+					echo "NUM_LIST value ${NUM_LIST} may not be calculated based on the actual execution time."
+					echo "Regenerate parallel list with NUM_MACHINES=6 for TARGET ${TARGET}."
+					PARALLEL_OPTIONS = PARALLEL_OPTIONS_TEMP + " NUM_MACHINES=6 TEST_TIME="
+					NUM_LIST = genParallelList(PARALLEL_OPTIONS)
 				}
 			} else {
 				PARALLEL_OPTIONS += " TEST_TIME= NUM_MACHINES="