diff --git a/src/location.c b/src/location.c
index dbcd67ec..9f929c00 100644
--- a/src/location.c
+++ b/src/location.c
@@ -421,12 +421,14 @@ location_caret (location loc, const char *style, FILE *out)
       {
         /* The last column to highlight.  Only the first line of
            multiline locations are quoted, in which case the ending
-           column is the end of line.  Single point locations (with
-           equal boundaries) denote the character that they
-           follow.  */
-        int col_end
+           column is the end of line.
+
+           We used to work with byte offsets, and that was much
+           easier.  However, we went back to using (visual) columns to
+           support truncating of long lines.  */
+        const int col_end
           = loc.start.line == loc.end.line
-          ? loc.end.column + (loc.start.column == loc.end.column)
+          ? loc.end.column
           : caret_info.line_len;
         /* Quote the file (at most the first line in the case of
            multiline locations).  */
@@ -436,24 +438,28 @@ location_caret (location loc, const char *style, FILE *out)
              expected (maybe the file was changed since the scanner
              ran), we might reach the end before we actually saw the
              opening column.  */
-          bool opened = false;
+          enum { before, inside, after } state = before;
           while (!mb_iseof (c) && !mb_iseq (c, '\n'))
             {
-              if (caret_info.pos.column == loc.start.column)
+              // We might have already opened (and even closed!) the
+              // style and yet have the equality of the columns if we
+              // just saw zero-width characters.
+              if (state == before
+                  && caret_info.pos.column == loc.start.column)
                 {
                   begin_use_class (style, out);
-                  opened = true;
+                  state = inside;
                 }
               if (skip < caret_info.pos.column)
                 mb_putc (c, out);
               boundary_compute (&caret_info.pos, mb_ptr (c), mb_len (c));
               caret_getc (c);
-              if (opened
+              if (state == inside
                   && (caret_info.pos.column == col_end
                       || width < caret_info.pos.column - skip))
                 {
                   end_use_class (style, out);
-                  opened = false;
+                  state = after;
                 }
               if (width < caret_info.pos.column - skip)
                 {
@@ -461,11 +467,11 @@ location_caret (location loc, const char *style, FILE *out)
                   break;
                 }
             }
-          // The line is shorter than expected.
-          if (opened)
+          if (state == inside)
             {
+              // The line is shorter than expected.
               end_use_class (style, out);
-              opened = false;
+              state = after;
             }
           putc ('\n', out);
         }
diff --git a/src/location.h b/src/location.h
index ccb42e3c..cb3025c6 100644
--- a/src/location.h
+++ b/src/location.h
@@ -42,16 +42,14 @@ typedef struct
 
   /* If positive, the column (starting at 1) just after the boundary.
      This is neither a byte count, nor a character count; it is a
-     column count.  If this is INT_MAX, the column number has
+     (visual) column count.  If this is INT_MAX, the column number has
      overflowed.
 
-     Meaningless and not displayed if nonpositive.
-  */
+     Meaningless and not displayed if nonpositive.  */
   int column;
 
-  /* If nonnegative, the byte number (starting at 0) in the current line.
-     Never displayed, used when printing error messages with colors to
-     know where colors start and end.  */
+  /* If nonnegative, the byte number (starting at 0) in the current
+     line.  Not displayed (unless --trace=location).  */
   int byte;
 
 } boundary;
diff --git a/tests/diagnostics.at b/tests/diagnostics.at
index cbf56b77..1471934f 100644
--- a/tests/diagnostics.at
+++ b/tests/diagnostics.at
@@ -37,15 +37,15 @@ AT_BISON_OPTION_PUSHDEFS
 
 AT_DATA_GRAMMAR([[input.y]], [$2])
 
+AT_DATA([experr], [$4])
+
 # For some reason, literal ^M in the input are removed and don't end
 # in `input.y`.  So use the two-character ^M represent it, and let
 # Perl insert real CR characters.
-if grep '\^M' input.y >/dev/null; then
-  AT_PERL_REQUIRE([-pi -e 's{\^M}{\r}gx' input.y])
+if $EGREP ['\^M|\\[0-9][0-9][0-9]'] input.y experr >/dev/null; then
+  AT_PERL_REQUIRE([-pi -e 's{\^M}{\r}g;s{\\(\d{3}|.)}{$v = $[]1; $v =~ /\A\d+\z/ ? chr($v) : $v}ge' input.y experr])
 fi
 
-AT_DATA([experr], [$4])
-
 AT_CHECK([LC_ALL="$locale" $5 bison -fcaret --color=debug -Wall input.y], [$3], [], [experr])
 
 # When no style, same messages, but without style.
@@ -193,6 +193,24 @@ input.y:12.8-10:     previous declaration
 ]])
 
 
+## ----------------------- ##
+## Zero-width characters.  ##
+## ----------------------- ##
+
+# We used to open twice the styling for characters that have a
+# zero-width on display (e.g., \005).
+
+AT_TEST([[Zero-width characters]],
+[[%%
+exp: an\005error.
+]],
+[1],
+[[input.y:10.8: <error>error:</error> invalid character: '\\005'
+   10 | exp: an<error>\005</error>error.
+      |        <error>^</error>
+]])
+
+
 ## -------------------------------------- ##
 ## Tabulations and multibyte characters.  ##
 ## -------------------------------------- ##