diff --git a/lucene/CHANGES.txt b/lucene/CHANGES.txt
index 30af545521c..b26e1cb50a7 100644
--- a/lucene/CHANGES.txt
+++ b/lucene/CHANGES.txt
@@ -232,6 +232,9 @@ Optimizations
   implementations. This improves random access as used by docvalues codecs
   if used with MMapDirectory.  (Robert Muir, Uwe Schindler)
 
+* LUCENE-5730: FSDirectory.open returns MMapDirectory for 64-bit operating
+  systems, not just Linux and Windows. (Robert Muir)
+
 Bug fixes
 
 * LUCENE-5673: MMapDirectory: Work around a "bug" in the JDK that throws
diff --git a/lucene/core/src/java/org/apache/lucene/store/FSDirectory.java b/lucene/core/src/java/org/apache/lucene/store/FSDirectory.java
index 2cbde59b6da..ed7968ab803 100644
--- a/lucene/core/src/java/org/apache/lucene/store/FSDirectory.java
+++ b/lucene/core/src/java/org/apache/lucene/store/FSDirectory.java
@@ -167,8 +167,7 @@ public abstract class FSDirectory extends BaseDirectory {
   /** Just like {@link #open(File)}, but allows you to
    *  also specify a custom {@link LockFactory}. */
   public static FSDirectory open(File path, LockFactory lockFactory) throws IOException {
-    if ((Constants.WINDOWS || Constants.SUN_OS || Constants.LINUX)
-          && Constants.JRE_IS_64BIT && MMapDirectory.UNMAP_SUPPORTED) {
+    if (Constants.JRE_IS_64BIT && MMapDirectory.UNMAP_SUPPORTED) {
       return new MMapDirectory(path, lockFactory);
     } else if (Constants.WINDOWS) {
       return new SimpleFSDirectory(path, lockFactory);