diff --git a/src/charset.c b/src/charset.c
index 8f058bd..5a2952c 100644
--- a/src/charset.c
+++ b/src/charset.c
@@ -207,7 +207,10 @@
 	    }
 	    while (c <= c2)
 	    {
-		if (!do_isalpha || isalpha(c)
+		/* Use the MB_ functions here, because isalpha() doesn't
+		 * work properly when 'encoding' is "latin1" and the locale is
+		 * "C".  */
+		if (!do_isalpha || MB_ISLOWER(c) || MB_ISUPPER(c)
 #ifdef FEAT_FKMAP
 			|| (p_altkeymap && (F_isalpha(c) || F_isdigit(c)))
 #endif
diff --git a/src/macros.h b/src/macros.h
index 400f771..f223099 100644
--- a/src/macros.h
+++ b/src/macros.h
@@ -54,10 +54,12 @@
 
 /*
  * toupper() and tolower() that use the current locale.
- * On some systems toupper()/tolower() only work on lower/uppercase characters
+ * On some systems toupper()/tolower() only work on lower/uppercase
+ * characters, first use islower() or isupper() then.
  * Careful: Only call TOUPPER_LOC() and TOLOWER_LOC() with a character in the
  * range 0 - 255.  toupper()/tolower() on some systems can't handle others.
- * Note: for UTF-8 use utf_toupper() and utf_tolower().
+ * Note: It is often better to use MB_TOLOWER() and MB_TOUPPER(), because many
+ * toupper() and tolower() implementations only work for ASCII.
  */
 #ifdef MSWIN
 #  define TOUPPER_LOC(c)	toupper_tab[(c) & 255]
diff --git a/src/version.c b/src/version.c
index 5f8faf8..11d9443 100644
--- a/src/version.c
+++ b/src/version.c
@@ -667,6 +667,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    79,
+/**/
     78,
 /**/
     77,