--- a/hotspot/src/share/vm/runtime/arguments.cpp	Mon Apr 10 20:10:09 2017 +0200
+++ b/hotspot/src/share/vm/runtime/arguments.cpp	Tue Apr 11 11:12:58 2017 +0200
@@ -734,6 +734,9 @@
   } else if (result->is_size_t()) {
     size_t size_t_v = (size_t) v;
     return CommandLineFlags::size_tAtPut(result, &size_t_v, origin) == Flag::SUCCESS;
+  } else if (result->is_double()) {
+    double double_v = (double) v;
+    return CommandLineFlags::doubleAtPut(result, &double_v, origin) == Flag::SUCCESS;
   } else {
     return false;
   }

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/test/runtime/CommandLine/DoubleFlagWithIntegerValue.java	Tue Apr 11 11:12:58 2017 +0200
@@ -0,0 +1,51 @@
+/*
+ * Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * 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 DoubleFlagWithIntegerValue
+ * @bug 8178364
+ * @summary Command-line flags of type double should accept integer values
+ * @library /test/lib
+ * @modules java.base/jdk.internal.misc
+ *          java.management
+ */
+
+import jdk.test.lib.process.ProcessTools;
+import jdk.test.lib.process.OutputAnalyzer;
+
+public class DoubleFlagWithIntegerValue {
+  public static void testDoubleFlagWithValue(String value) throws Exception {
+    ProcessBuilder pb = ProcessTools.createJavaProcessBuilder("-XX:G1ConcMarkStepDurationMillis=" + value, "-version");
+    OutputAnalyzer output = new OutputAnalyzer(pb.start());
+    output.shouldNotContain("Improperly specified VM option");
+    output.shouldHaveExitValue(0);
+  }
+
+  public static void main(String[] args) throws Exception {
+    // Test double format
+    testDoubleFlagWithValue("10.0");
+
+    // Test integer format
+    testDoubleFlagWithValue("10");
+  }
+}