--- a/scripts/plot/private/__pltopt__.m
+++ b/scripts/plot/private/__pltopt__.m
@@ -112,7 +112,7 @@
     for i = nel:-1:1
       [options(i), valid] = __pltopt1__ (caller, opt{i}, err_on_invalid);
       if (! err_on_invalid && ! valid)
-	return;
+        return;
       endif
     endfor
   else
@@ -152,7 +152,7 @@
     elseif (strncmp (opt, "#~", 2) || strncmp (opt, "~>", 2))
       n = 2;
     elseif (strncmp (opt, "~", 1) || strncmp (opt, ">", 1) 
-	    || strncmp (opt, "#", 1))
+            || strncmp (opt, "#", 1))
       n = 1;
     endif
     options.linestyle = opt(1:n);
@@ -169,60 +169,60 @@
       topt = opt(1);
       n = 1;
       if (topt == "-" || topt == ":")
-	have_linestyle = true;
-	options.linestyle = topt;
+        have_linestyle = true;
+        options.linestyle = topt;
       elseif (topt == "+" || topt == "o" || topt == "*"
-	      || topt == "." || topt == "x" || topt == "s"
-	      || topt == "d" || topt == "^" || topt == "v"
-	      || topt == ">" || topt == "<" || topt == "p"
-	      || topt == "h" || topt == "@")
-	have_marker = true;
+              || topt == "." || topt == "x" || topt == "s"
+              || topt == "d" || topt == "^" || topt == "v"
+              || topt == ">" || topt == "<" || topt == "p"
+              || topt == "h" || topt == "@")
+        have_marker = true;
         ## Backward compatibility.  Leave undocumented.
-	if (topt == "@")
-	  topt = "+";
-	endif
-	options.marker = topt;
+        if (topt == "@")
+          topt = "+";
+        endif
+        options.marker = topt;
 ### Numeric color specs for backward compatibility.  Leave undocumented.
       elseif (topt == "k" || topt == "0")
-	options.color = [0, 0, 0];
+        options.color = [0, 0, 0];
       elseif (topt == "r" || topt == "1")
-	options.color = [1, 0, 0];
+        options.color = [1, 0, 0];
       elseif (topt == "g" || topt == "2")
-	options.color = [0, 1, 0];
+        options.color = [0, 1, 0];
       elseif (topt == "b" || topt == "3")
-	options.color = [0, 0, 1];
+        options.color = [0, 0, 1];
       elseif (topt == "y")
-	options.color = [1, 1, 0];
+        options.color = [1, 1, 0];
       elseif (topt == "m" || topt == "4")
-	options.color = [1, 0, 1];
+        options.color = [1, 0, 1];
       elseif (topt == "c" || topt == "5")
-	options.color = [0, 1, 1];
+        options.color = [0, 1, 1];
       elseif (topt == "w" || topt == "6")
-	options.color = [1, 1, 1];
+        options.color = [1, 1, 1];
       elseif (isspace (topt))
-	## Do nothing.
+        ## Do nothing.
       elseif (topt == ";")
-	t = index (opt(2:end), ";");
-	if (t)
-	  options.key = undo_string_escapes (opt(2:t));
-	  n = t+1;
-	else
-	  if (err_on_invalid)
+        t = index (opt(2:end), ";");
+        if (t)
+          options.key = undo_string_escapes (opt(2:t));
+          n = t+1;
+        else
+          if (err_on_invalid)
             error ("%s: unfinished key label", caller);
-	  else
-	    valid = false;
-	    options = __default_plot_options__ ();
-	    return;
-	  endif
+          else
+            valid = false;
+            options = __default_plot_options__ ();
+            return;
+          endif
         endif
       else
-	if (err_on_invalid)
-	  error ("%s: unrecognized format character: `%s'", caller, topt);
-	else
-	  valid = false;
-	  options = __default_plot_options__ ();
-	  return;
-	endif
+        if (err_on_invalid)
+          error ("%s: unrecognized format character: `%s'", caller, topt);
+        else
+          valid = false;
+          options = __default_plot_options__ ();
+          return;
+        endif
       endif
     endif
     opt(1:n) = [];