diff --git a/7.3.521 b/7.3.521
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+To: vim_dev@googlegroups.com
+Subject: Patch 7.3.521
+Fcc: outbox
+From: Bram Moolenaar <Bram@moolenaar.net>
+Mime-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+------------
+
+Patch 7.3.521
+Problem:    Using "z=" on a multi-byte character may cause a crash.
+Solution:   Don't use strlen() on an int pointer.
+Files:	    src/spell.c
+
+
+*** ../vim-7.3.520/src/spell.c	2012-01-10 22:26:12.000000000 +0100
+--- src/spell.c	2012-05-18 18:01:58.000000000 +0200
+***************
+*** 14494,14506 ****
+      int		p0 = -333;
+      int		c0;
+      int		did_white = FALSE;
+  
+      /*
+       * Convert the multi-byte string to a wide-character string.
+       * Remove accents, if wanted.  We actually remove all non-word characters.
+       * But keep white space.
+       */
+!     n = 0;
+      for (s = inword; *s != NUL; )
+      {
+  	t = s;
+--- 14494,14508 ----
+      int		p0 = -333;
+      int		c0;
+      int		did_white = FALSE;
++     int		wordlen;
++ 
+  
+      /*
+       * Convert the multi-byte string to a wide-character string.
+       * Remove accents, if wanted.  We actually remove all non-word characters.
+       * But keep white space.
+       */
+!     wordlen = 0;
+      for (s = inword; *s != NUL; )
+      {
+  	t = s;
+***************
+*** 14521,14532 ****
+  		    continue;
+  	    }
+  	}
+! 	word[n++] = c;
+      }
+!     word[n] = NUL;
+  
+      /*
+!      * This comes from Aspell phonet.cpp.
+       * Converted from C++ to C.  Added support for multi-byte chars.
+       * Changed to keep spaces.
+       */
+--- 14523,14534 ----
+  		    continue;
+  	    }
+  	}
+! 	word[wordlen++] = c;
+      }
+!     word[wordlen] = NUL;
+  
+      /*
+!      * This algorithm comes from Aspell phonet.cpp.
+       * Converted from C++ to C.  Added support for multi-byte chars.
+       * Changed to keep spaces.
+       */
+***************
+*** 14711,14717 ****
+  			    }
+  			if (k > k0)
+  			    mch_memmove(word + i + k0, word + i + k,
+! 				    sizeof(int) * (STRLEN(word + i + k) + 1));
+  
+  			/* new "actual letter" */
+  			c = word[i];
+--- 14713,14719 ----
+  			    }
+  			if (k > k0)
+  			    mch_memmove(word + i + k0, word + i + k,
+! 				    sizeof(int) * (wordlen - (i + k) + 1));
+  
+  			/* new "actual letter" */
+  			c = word[i];
+***************
+*** 14739,14745 ****
+  			    if (c != NUL)
+  				wres[reslen++] = c;
+  			    mch_memmove(word, word + i + 1,
+! 				    sizeof(int) * (STRLEN(word + i + 1) + 1));
+  			    i = 0;
+  			    z0 = 1;
+  			}
+--- 14741,14747 ----
+  			    if (c != NUL)
+  				wres[reslen++] = c;
+  			    mch_memmove(word, word + i + 1,
+! 				       sizeof(int) * (wordlen - (i + 1) + 1));
+  			    i = 0;
+  			    z0 = 1;
+  			}
+*** ../vim-7.3.520/src/version.c	2012-05-18 17:03:14.000000000 +0200
+--- src/version.c	2012-05-18 18:06:29.000000000 +0200
+***************
+*** 716,717 ****
+--- 716,719 ----
+  {   /* Add new patch number below this line */
++ /**/
++     521,
+  /**/
+
+-- 
+OLD WOMAN: King of the WHO?
+ARTHUR:    The Britons.
+OLD WOMAN: Who are the Britons?
+                 "Monty Python and the Holy Grail" PYTHON (MONTY) PICTURES LTD
+
+ /// Bram Moolenaar -- Bram@Moolenaar.net -- http://www.Moolenaar.net   \\\
+///        sponsor Vim, vote for features -- http://www.Vim.org/sponsor/ \\\
+\\\  an exciting new programming language -- http://www.Zimbu.org        ///
+ \\\            help me help AIDS victims -- http://ICCF-Holland.org    ///