src/java.desktop/macosx/classes/com/apple/laf/AquaLabelUI.java

*** 58,68 ****
          if (AquaMnemonicHandler.isMnemonicHidden()) {
              mnemIndex = -1;
          }
  
          g.setColor(l.getForeground());
!         SwingUtilities2.drawStringUnderlineCharAt(l, g, s, mnemIndex, textX, textY);
      }
  
      /**
       * Paint clippedText at textX, textY with background.lighter() and then
       * shifted down and to the right by one pixel with background.darker().
--- 58,68 ----
          if (AquaMnemonicHandler.isMnemonicHidden()) {
              mnemIndex = -1;
          }
  
          g.setColor(l.getForeground());
!         getTextUIDrawing().drawStringUnderlineCharAt(l, g, s, mnemIndex, textX, textY);
      }
  
      /**
       * Paint clippedText at textX, textY with background.lighter() and then
       * shifted down and to the right by one pixel with background.darker().
*** 79,89 ****
          final Color background = l.getBackground();
  
          // if our background is still something we set then we can use our happy background color.
          if (background instanceof UIResource) {
              g.setColor(getDisabledLabelColor(l));
!             SwingUtilities2.drawStringUnderlineCharAt(l, g, s, accChar, textX, textY);
          } else {
              super.paintDisabledText(l, g, s, textX, textY);
          }
      }
  
--- 79,89 ----
          final Color background = l.getBackground();
  
          // if our background is still something we set then we can use our happy background color.
          if (background instanceof UIResource) {
              g.setColor(getDisabledLabelColor(l));
!             getTextUIDrawing().drawStringUnderlineCharAt(l, g, s, accChar, textX, textY);
          } else {
              super.paintDisabledText(l, g, s, textX, textY);
          }
      }