diff --git a/doctoc.js b/doctoc.js
index d28bd56b..0e9a6c20 100755
--- a/doctoc.js
+++ b/doctoc.js
@@ -73,7 +73,7 @@ function transformAndSave(files, mode, maxHeaderLevel, minHeaderLevel, minTocIte
 function printUsageAndExit(isErr) {
   var outputFunc = isErr ? log.error : log.info;
 
-  outputFunc('Usage: doctoc [mode] [--entryprefix prefix] [--notitle | --title title] [--maxlevel level] [--minlevel level] [--mintocitems qty] [--toc-pragma-style style] [--toc-header-content content] [--toc-footer-content content] [--toc-items-indentation-width width] [--all] [--loglevel level] [--update-only] [--syntax (' + supportedSyntaxes.join("|") + ')] <path> (where path is some path to a directory (e.g., .) or a file (e.g., README.md))');
+  outputFunc('Usage: doctoc [mode] [--entryprefix prefix] [--notitle | --title title] [--maxlevel level] [--minlevel level] [--mintocitems qty] [--toc-pragma-style style] [--toc-header-content content] [--toc-footer-content content] [--toc-items-indentation-width width] [--toc-items-indentation-style style][--all] [--loglevel level] [--update-only] [--syntax (' + supportedSyntaxes.join("|") + ')] <path> (where path is some path to a directory (e.g., .) or a file (e.g., README.md))');
   outputFunc('\nAvailable modes are:');
   for (var key in modes) {
     outputFunc("  --%s\t%s", key, modes[key]);
@@ -97,7 +97,7 @@ var mode = modes["github"];
 var argv = minimist(process.argv.slice(2),
     {
       boolean: [ 'h', 'help', 'T', 'notitle', 's', 'stdout', 'all' , 'u', 'update-only', 'd', 'dryrun'].concat(Object.keys(modes)),
-      string: [ 'title', 't', 'maxlevel', 'm', 'minlevel', 'entryprefix', 'syntax', 'mintocitems', 'toc-title-padding-before', 'toc-header-content', 'toc-footer-content', 'toc-pragma-style', 'toc-items-indentation-width', 'document-lines-min', 'l', 'loglevel' ],
+      string: [ 'title', 't', 'maxlevel', 'm', 'minlevel', 'entryprefix', 'syntax', 'mintocitems', 'toc-title-padding-before', 'toc-header-content', 'toc-footer-content', 'toc-pragma-style', 'toc-items-indentation-width', 'toc-items-indentation-style', 'document-lines-min', 'l', 'loglevel' ],
       unknown: function(a) { return (a[0] == '-' ? (console.error('Unknown option(s): ' + a), printUsageAndExit(true)) : true); }
     });
 
@@ -158,6 +158,9 @@ var indentWidth = argv['toc-items-indentation-width'];
 if (indentWidth !== undefined && isNaN(indentWidth)) { log.error('ToC indentation width: ' + indentWidth + ' is not a number'), printUsageAndExit(true); }
 else if (indentWidth === undefined) { indentWidth = (mode === 'bitbucket.org' || mode === 'gitlab.com') ? 4 : 2; }
 
+var indentStyle = argv['toc-items-indentation-style'];
+if (indentStyle && indentStyle !== 'space' && indentStyle !== 'tab') { log.error('Indentation style not supported: ' + indentStyle), printUsageAndExit(true); }
+
 var minLines = argv['document-lines-min'] || 0;
 if (isNaN(minLines)) { log.error('Document min lines: ' + minLines + ' is not a number'), printUsageAndExit(true); }
 
@@ -177,6 +180,7 @@ var options = {
     items: {
       indentation:{
         width: indentWidth,
+        style: indentStyle,
       }
     },
     title: {
diff --git a/lib/transform.js b/lib/transform.js
index 205729a7..ef56600a 100644
--- a/lib/transform.js
+++ b/lib/transform.js
@@ -178,7 +178,14 @@ function detectLineEnding(content, defaultEol) {
 }
 
 exports = module.exports = function transform(content, mode, maxHeaderLevel, minHeaderLevel, minTocItems, title, notitle, entryPrefix, processAll, updateOnly, syntax, options) {
+  options ??= {};
+  options.toc ??= {};
+  options.toc.items ??= {};
+  options.toc.items.indentation ??= {};
+
   syntax = syntax || "md";
+  options.toc.items.indentation.style ??= 'space';
+  options.toc.items.indentation.width ??= (mode === 'bitbucket.org' || mode === 'gitlab.com') ? 4 : 2;
   var eol = '\n';
   eol = detectLineEnding(content, eol);
   var skipTag = contentGenerator.skipTag(syntax) + eol;
@@ -262,13 +269,7 @@ exports = module.exports = function transform(content, mode, maxHeaderLevel, min
     var allHeaders = processHeaders(headers, mode);
     var lowestRank = allHeaders.reduce((min, h) => Math.min(min, h.rank), Infinity);
     
-    var indentation = ' ';
-    var indentationWidth = options?.toc?.items?.indentation?.width;
-    // remove this fallback based on mode in v3
-    if(indentationWidth === undefined){
-      // 4 spaces required for proper indention on Bitbucket and GitLab
-      indentationWidth = (mode === 'bitbucket.org' || mode === 'gitlab.com') ? 4 : 2;
-    }
+    var indentation = options.toc.items.indentation.style === 'tab' ? '\t' : ' ';
 
     if (options?.toc?.header?.content) { tocLines.push(options.toc.header.content); }
     if (padTitle && inferredTitle) { tocLines.push(''); }
@@ -277,7 +278,7 @@ exports = module.exports = function transform(content, mode, maxHeaderLevel, min
 
     tocLines.push(...allHeaders
         .map(function (x) {
-          return indentation.repeat((x.rank - lowestRank) * indentationWidth) + entryPrefix + ' ' + x.anchor;
+          return indentation.repeat((x.rank - lowestRank) * options.toc.items.indentation.width) + entryPrefix + ' ' + x.anchor;
         }));
 
     tocLines.push('');