diff -r b96683be2713 -r 5667388e3a79 jdk/src/java.base/windows/classes/sun/nio/fs/WindowsPath.java
--- a/jdk/src/java.base/windows/classes/sun/nio/fs/WindowsPath.java	Fri Feb 06 09:57:28 2015 +0100
+++ b/jdk/src/java.base/windows/classes/sun/nio/fs/WindowsPath.java	Fri Feb 06 08:05:44 2015 -0800
@@ -391,6 +391,10 @@
         if (!this.root.equalsIgnoreCase(other.root))
             throw new IllegalArgumentException("'other' has different root");
 
+        // this path is the empty path
+        if (this.isEmpty())
+            return other;
+
         int bn = this.getNameCount();
         int cn = other.getNameCount();