--- a/src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp	Mon Apr 08 12:19:51 2019 -0400
+++ b/src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp	Mon Apr 08 18:42:27 2019 +0200
@@ -1204,7 +1204,9 @@
 
 void ShenandoahHeap::gc_threads_do(ThreadClosure* tcl) const {
   workers()->threads_do(tcl);
-  _safepoint_workers->threads_do(tcl);
+  if (_safepoint_workers != NULL) {
+    _safepoint_workers->threads_do(tcl);
+  }
   if (ShenandoahStringDedup::is_enabled()) {
     ShenandoahStringDedup::threads_do(tcl);
   }

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/hotspot/jtreg/gc/shenandoah/options/TestSafepointWorkers.java	Mon Apr 08 18:42:27 2019 +0200
@@ -0,0 +1,46 @@
+/*
+ * Copyright (c) 2019, Red Hat, Inc. All rights reserved.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+/*
+ * @test TestSingleSafepointWorker
+ * @key gc
+ * @requires vm.gc.Shenandoah
+ *
+ * @run main/othervm -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -XX:ShenandoahParallelSafepointThreads=1 -Xmx128m TestSafepointWorkers
+ * @run main/othervm -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -XX:ShenandoahParallelSafepointThreads=2 -Xmx128m TestSafepointWorkers
+ * @run main/othervm -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -XX:ShenandoahParallelSafepointThreads=4 -Xmx128m TestSafepointWorkers
+ * @run main/othervm -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -XX:ShenandoahParallelSafepointThreads=8 -Xmx128m TestSafepointWorkers
+ */
+
+public class TestSafepointWorkers {
+    static final long TARGET_MB = Long.getLong("target", 1000); // 1 Gb allocation
+
+    static volatile Object sink;
+
+    public static void main(String[] args) throws Exception {
+        long count = TARGET_MB * 1024 * 1024 / 16;
+        for (long c = 0; c < count; c++) {
+            sink = new Object();
+        }
+    }
+}