--- old/modules/javafx.controls/src/main/java/javafx/scene/control/skin/LabeledSkinBase.java	2017-10-17 16:47:02.304027999 +0530
+++ new/modules/javafx.controls/src/main/java/javafx/scene/control/skin/LabeledSkinBase.java	2017-10-17 16:47:02.083918000 +0530
@@ -25,6 +25,7 @@
 
 package javafx.scene.control.skin;
 
+import javafx.geometry.Point2D;
 import com.sun.javafx.scene.control.LabeledText;
 import com.sun.javafx.scene.control.behavior.TextBinding;
 import com.sun.javafx.scene.control.skin.Utils;
@@ -573,13 +574,13 @@
             contentY = (y + ((h - contentHeight) / 2.0));
         }
 
-        double preMnemonicWidth = 0.0;
+        Point2D mnemonicPos = null;
         double mnemonicWidth = 0.0;
         double mnemonicHeight = 0.0;
         if (containsMnemonic) {
             final Font font = text.getFont();
             String preSt = bindings.getText();
-            preMnemonicWidth = Utils.computeTextWidth(font, preSt.substring(0, bindings.getMnemonicIndex()), 0);
+            mnemonicPos = Utils.computeMnemonicPosition(font, preSt, bindings.getMnemonicIndex(), this.wrapWidth, labeled.getLineSpacing());
             mnemonicWidth = Utils.computeTextWidth(font, preSt.substring(bindings.getMnemonicIndex(), bindings.getMnemonicIndex() + 1), 0);
             mnemonicHeight = Utils.computeTextHeight(font, "_", 0, text.getBoundsType());
         }
@@ -612,9 +613,9 @@
             // adjust the text based on the text's minX/minY so no need to
             // worry about that here
             text.relocate(snapPositionX(contentX), snapPositionY(contentY));
-            if (containsMnemonic) {
+            if (containsMnemonic && (mnemonicPos != null)) {
                 mnemonic_underscore.setEndX(mnemonicWidth-2.0);
-                mnemonic_underscore.relocate(contentX+preMnemonicWidth, contentY+mnemonicHeight-1);
+                mnemonic_underscore.relocate(contentX + mnemonicPos.getX(), contentY + mnemonicPos.getY());
             }
 
         } else if (ignoreText) {
@@ -623,11 +624,10 @@
             // there is a graphic, the text isn't even in the scene)
             text.relocate(snapPositionX(contentX), snapPositionY(contentY));
             graphic.relocate(snapPositionX(contentX), snapPositionY(contentY));
-            if (containsMnemonic) {
+            if (containsMnemonic && (mnemonicPos != null)) {
                 mnemonic_underscore.setEndX(mnemonicWidth);
                 mnemonic_underscore.setStrokeWidth(mnemonicHeight/10.0);
-                mnemonic_underscore.relocate(contentX+preMnemonicWidth, contentY+mnemonicHeight-1);
-
+                mnemonic_underscore.relocate(contentX + mnemonicPos.getX(), contentY + mnemonicPos.getY());
             }
         } else {
             // There is both text and a graphic, so I need to position them
@@ -670,10 +670,10 @@
                 textY = contentY + ((contentHeight - textHeight) / 2.0);
             }
             text.relocate(snapPositionX(textX), snapPositionY(textY));
-            if (containsMnemonic) {
+            if (containsMnemonic && (mnemonicPos != null)) {
                 mnemonic_underscore.setEndX(mnemonicWidth);
                 mnemonic_underscore.setStrokeWidth(mnemonicHeight/10.0);
-                mnemonic_underscore.relocate(snapPositionX(textX+preMnemonicWidth), snapPositionY(textY+mnemonicHeight-1));
+                mnemonic_underscore.relocate(textX + mnemonicPos.getX(), textY + mnemonicPos.getY());
             }
             graphic.relocate(snapPositionX(graphicX), snapPositionY(graphicY));
         }
--- old/modules/javafx.controls/src/main/java/com/sun/javafx/scene/control/skin/Utils.java	2017-10-17 16:47:02.976364000 +0530
+++ new/modules/javafx.controls/src/main/java/com/sun/javafx/scene/control/skin/Utils.java	2017-10-17 16:47:02.756254000 +0530
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2011, 2016, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2011, 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
@@ -146,6 +146,51 @@
         return layout.getBounds().getHeight();
     }
 
+    public static Point2D computeMnemonicPosition(Font font, String text, int mnemonicIndex, double wrappingWidth,
+                                                  double lineSpacing) {
+        // Input validation
+        if ((font == null) || (text == null) ||
+            (mnemonicIndex < 0) || (mnemonicIndex > text.length())) {
+            return  null;
+        }
+
+        // Layout the text with given font, wrapping width and line spacing
+        layout.setContent(text, FontHelper.getNativeFont(font));
+        layout.setWrapWidth((float)wrappingWidth);
+        layout.setLineSpacing((float)lineSpacing);
+
+        // The text could be spread over multiple lines
+        // We need to find out on which line the mnemonic character lies
+        int start = 0;
+        int i = 0;
+        int totalLines = layout.getLines().length;
+        while (i < totalLines) {
+            int lineLength =  layout.getLines()[i].getLength();
+
+            if ((mnemonicIndex >= start) &&
+                (mnemonicIndex < (start + lineLength))) {
+                // mnemonic lies on line 'i'
+                break;
+            }
+
+            start = start + lineLength;
+            i++;
+        }
+
+        // Find x and y offsets of mnemonic character position
+        // in line numbered 'i'
+        double lineHeight = layout.getBounds().getHeight() / totalLines;
+        double x = Utils.computeTextWidth(font, text.substring(start, mnemonicIndex), 0 );
+
+        double y = (lineHeight * (i+1));
+        // Adjust y offset for linespacing except for the last line.
+        if ((i+1) != totalLines) {
+            y = y - (lineSpacing / 2);
+        }
+
+        return new Point2D(x, y);
+    }
+
     public static int computeTruncationIndex(Font font, String text, double width) {
         helper.setText(text);
         helper.setFont(font);