--- a/libinterp/corefcn/file-io.cc	Fri Nov 24 18:14:37 2017 +0100
+++ b/libinterp/corefcn/file-io.cc	Fri Nov 24 17:29:00 2017 -0800
@@ -2210,6 +2210,17 @@
 
 ## Check for delimiter after exponent
 %!assert (textscan ("1e-3|42", "%f", "delimiter", "|"), {[1e-3; 42]})
+
+%!test <*52479>
+%! str = "\t\ta\tb\tc\n";
+%! ret = textscan (str, "%s", "delimiter", "\t");
+%! assert (ret, { {''; ''; 'a'; 'b'; 'c'} }) ;
+
+%!test <*52479>
+%! str = "\t\ta\tb\tc\n";
+%! ret = textscan (str, "%s", "delimiter", {"\t"});
+%! assert (ret, { {''; ''; 'a'; 'b'; 'c'} }) ;
+
 */
 
 // These tests have end-comment sequences, so can't just be in a comment

--- a/libinterp/corefcn/oct-stream.cc	Fri Nov 24 18:14:37 2017 +0100
+++ b/libinterp/corefcn/oct-stream.cc	Fri Nov 24 17:29:00 2017 -0800
@@ -29,6 +29,7 @@
 #include <cctype>
 #include <cstring>
 
+#include <algorithm>
 #include <deque>
 #include <fstream>
 #include <iomanip>
@@ -3714,6 +3715,24 @@
           error ("%s: unrecognized option '%s'", who.c_str (), param.c_str ());
       }
 
+    // Remove any user-supplied delimiter from whitespace list
+    for (unsigned int j = 0; j < delims.length (); j++)
+      {
+        whitespace.erase (std::remove (whitespace.begin (),
+                                       whitespace.end (),
+                                       delims[j]),
+                          whitespace.end ());
+      }
+    for (int j = 0; j < delim_list.numel (); j++)
+      {
+        std::string delim = delim_list(j).string_value ();
+        if (delim.length () == 1)
+          whitespace.erase (std::remove (whitespace.begin (), 
+                                         whitespace.end (),
+                                         delim[0]),
+                            whitespace.end ());
+      }
+
     whitespace_table = std::string (256, '\0');
     for (unsigned int i = 0; i < whitespace.length (); i++)
       whitespace_table[whitespace[i]] = '1';