Index: freetype-2.5.5/src/base/ftsynth.c
===================================================================
--- freetype-2.5.5.orig/src/base/ftsynth.c	2014-11-26 18:45:48.000000000 +0100
+++ freetype-2.5.5/src/base/ftsynth.c	2015-02-14 11:46:28.929503116 +0100
@@ -150,7 +150,10 @@
 
     slot->metrics.width        += xstr;
     slot->metrics.height       += ystr;
-    slot->metrics.horiAdvance  += xstr;
+    /* for mono-width fonts (like Andale, Courier, etc.) we need */
+    /* to keep the original advance width                        */
+    if ( !FT_IS_FIXED_WIDTH( face ) )
+      slot->metrics.horiAdvance  += xstr;
     slot->metrics.vertAdvance  += ystr;
     slot->metrics.horiBearingY += ystr;
 
Index: freetype-2.5.5/include/ftsynth.h
===================================================================
--- freetype-2.5.5.orig/include/ftsynth.h	2014-12-02 13:11:52.000000000 +0100
+++ freetype-2.5.5/include/ftsynth.h	2015-02-14 13:12:50.014546469 +0100
@@ -62,8 +62,10 @@
   /* a wrapper for @FT_Outline_Embolden and @FT_Bitmap_Embolden.           */
   /*                                                                       */
   /* For emboldened outlines the height, width, and advance metrics are    */
-  /* increased by the strength of the emboldening.  You can also call      */
-  /* @FT_Outline_Get_CBox to get precise values.                           */
+  /* increased by the strength of the emboldening.  (An exception to this  */
+  /* are mono-width fonts, where the horizontal advance metrics are left   */
+  /* unchanged.)  You can also call @FT_Outline_Get_CBox to get precise    */
+  /* values.                                                               */
   FT_EXPORT( void )
   FT_GlyphSlot_Embolden( FT_GlyphSlot  slot );