--- old/src/java.base/share/classes/java/nio/file/Files.java	2018-06-25 21:32:56.402338674 -0700
+++ new/src/java.base/share/classes/java/nio/file/Files.java	2018-06-25 21:32:55.970291730 -0700
@@ -43,7 +43,9 @@
 import java.nio.charset.Charset;
 import java.nio.charset.CharsetDecoder;
 import java.nio.charset.CharsetEncoder;
+import java.nio.charset.MalformedInputException;
 import java.nio.charset.StandardCharsets;
+import java.nio.charset.UnmappableCharacterException;
 import java.nio.file.attribute.BasicFileAttributeView;
 import java.nio.file.attribute.BasicFileAttributes;
 import java.nio.file.attribute.DosFileAttributes;   // javadoc
@@ -3282,6 +3284,10 @@
         try {
             return JLA.newStringNoRepl(ba, cs);
         } catch (IllegalArgumentException e) {
+            Throwable cause = e.getCause();
+            if (cause != null && cause instanceof MalformedInputException) {
+                throw (MalformedInputException)cause;
+            }
             throw new IOException(e);
         }
     }
@@ -3638,6 +3644,10 @@
             byte[] bytes = JLA.getBytesNoRepl(String.valueOf(csq), cs);
             write(path, bytes, options);
         } catch (IllegalArgumentException e) {
+            Throwable cause = e.getCause();
+            if (cause != null && cause instanceof UnmappableCharacterException) {
+                throw (UnmappableCharacterException)cause;
+            }
             throw new IOException(e);
         }