diff --git a/src/md4c.c b/src/md4c.c
index 136edce..5be3809 100644
--- a/src/md4c.c
+++ b/src/md4c.c
@@ -5041,7 +5041,9 @@ md_process_all_blocks(MD_CTX* ctx)
             if(block->flags & MD_BLOCK_CONTAINER_CLOSER) {
                 MD_LEAVE_BLOCK(block->type, &det);
 
-                if(block->type == MD_BLOCK_UL || block->type == MD_BLOCK_OL || block->type == MD_BLOCK_QUOTE || block->type == MD_BLOCK_BOX)
+                if(block->type == MD_BLOCK_UL || block->type == MD_BLOCK_OL
+                        || block->type == MD_BLOCK_QUOTE || block->type == MD_BLOCK_BOX
+                        || block->type == MD_BLOCK_INDENT)
                     ctx->n_containers--;
             }
 
@@ -5051,7 +5053,8 @@ md_process_all_blocks(MD_CTX* ctx)
                 if(block->type == MD_BLOCK_UL || block->type == MD_BLOCK_OL) {
                     ctx->containers[ctx->n_containers].is_loose = (block->flags & MD_BLOCK_LOOSE_LIST);
                     ctx->n_containers++;
-                } else if(block->type == MD_BLOCK_QUOTE || block->type == MD_BLOCK_BOX) {
+                } else if(block->type == MD_BLOCK_QUOTE || block->type == MD_BLOCK_BOX
+                        || block->type == MD_BLOCK_INDENT) {
                     /* This causes that any text in a block quote, even if
                      * nested inside a tight list item, is wrapped with
                      * <p>...</p>. */
@@ -5749,6 +5752,9 @@ md_is_container_compatible(const MD_CONTAINER* pivot, const MD_CONTAINER* contai
     if(container->ch == _T('!'))
         return FALSE;
 
+    if(container->ch == _T(':'))
+        return FALSE;
+
     if(container->ch != pivot->ch)
         return FALSE;
     if(container->mark_indent > pivot->contents_indent)
@@ -5820,6 +5826,10 @@ md_enter_child_containers(MD_CTX* ctx, int n_children, MD_LINE_ANALYSIS* line)
                 MD_CHECK(md_push_box_bytes(ctx, line, MD_BLOCK_CONTAINER_OPENER));
                 break;
 
+            case _T(':'):
+                MD_CHECK(md_push_container_bytes(ctx, MD_BLOCK_INDENT, 0, 0, MD_BLOCK_CONTAINER_OPENER));
+                break;
+
             default:
                 MD_UNREACHABLE();
                 break;
@@ -5866,6 +5876,11 @@ md_leave_child_containers(MD_CTX* ctx, int n_keep)
                                 0, MD_BLOCK_CONTAINER_CLOSER));
                 break;
 
+            case _T(':'):
+                MD_CHECK(md_push_container_bytes(ctx, MD_BLOCK_INDENT, 0,
+                                0, MD_BLOCK_CONTAINER_CLOSER));
+                break;
+
             default:
                 MD_UNREACHABLE();
                 break;
@@ -5911,6 +5926,18 @@ md_is_container_mark(MD_CTX* ctx, unsigned indent, OFF beg, OFF* p_end, MD_CONTA
         return TRUE;
     }
 
+    /* Check for indent mark. */
+    if(CH(off) == _T(':')) {
+        off++;
+        p_container->ch = _T(':');
+        p_container->is_loose = FALSE;
+        p_container->is_task = FALSE;
+        p_container->mark_indent = indent;
+        p_container->contents_indent = indent + 1;
+        *p_end = off;
+        return TRUE;
+    }
+
     /* Check for list item bullet mark. */
     if(ISANYOF(off, _T("-+*"))  &&  (off+1 >= ctx->size || ISBLANK(off+1) || ISNEWLINE(off+1))) {
         p_container->ch = CH(off);
@@ -5997,7 +6024,10 @@ md_analyze_line(MD_CTX* ctx, OFF beg, OFF* p_end,
              off < ctx->size  &&  CH(off) == _T('>'))
                 ||
            (c->ch == _T('!')  &&  line->indent < ctx->code_indent_offset  &&
-             off < ctx->size  &&  CH(off) == _T('!')))
+             off < ctx->size  &&  CH(off) == _T('!'))
+                ||
+           (c->ch == _T(':')  &&  line->indent < ctx->code_indent_offset  &&
+             off < ctx->size  &&  CH(off) == _T(':')))
         {
             /* Block quote mark. */
             off++;
@@ -6011,7 +6041,7 @@ md_analyze_line(MD_CTX* ctx, OFF beg, OFF* p_end,
 
             line->beg = off;
 
-        } else if(c->ch != _T('>')  &&  c->ch != _T('!')
+        } else if(c->ch != _T('>')  &&  c->ch != _T('!')  &&  c->ch != _T(':')
                 &&  line->indent >= c->contents_indent) {
             /* List. */
             line->indent -= c->contents_indent;
@@ -6028,7 +6058,8 @@ md_analyze_line(MD_CTX* ctx, OFF beg, OFF* p_end,
         if(n_brothers + n_children == 0) {
             while(n_parents < ctx->n_containers
                     &&  ctx->containers[n_parents].ch != _T('>')
-                    &&  ctx->containers[n_parents].ch != _T('!'))
+                    &&  ctx->containers[n_parents].ch != _T('!')
+                    &&  ctx->containers[n_parents].ch != _T(':'))
                 n_parents++;
         }
     }
@@ -6104,7 +6135,8 @@ md_analyze_line(MD_CTX* ctx, OFF beg, OFF* p_end,
                 ctx->last_line_has_list_loosening_effect = (n_parents > 0  &&
                         n_brothers + n_children == 0  &&
                         ctx->containers[n_parents-1].ch != _T('>') &&
-                        ctx->containers[n_parents-1].ch != _T('!'));
+                        ctx->containers[n_parents-1].ch != _T('!') &&
+                        ctx->containers[n_parents-1].ch != _T(':'));
 
     #if 1
                 /* See https://github.com/mity/md4c/issues/6
@@ -6120,6 +6152,7 @@ md_analyze_line(MD_CTX* ctx, OFF beg, OFF* p_end,
                  */
                 if(n_parents > 0  &&  ctx->containers[n_parents-1].ch != _T('>')  &&
                    ctx->containers[n_parents-1].ch != _T('!') &&
+                   ctx->containers[n_parents-1].ch != _T(':') &&
                    n_brothers + n_children == 0  &&  ctx->current_block == NULL  &&
                    ctx->n_block_bytes > (int) sizeof(MD_BLOCK))
                 {
@@ -6140,6 +6173,7 @@ md_analyze_line(MD_CTX* ctx, OFF beg, OFF* p_end,
             if(ctx->last_list_item_starts_with_two_blank_lines) {
                 if(n_parents > 0  &&  ctx->containers[n_parents-1].ch != _T('>')  &&
                    ctx->containers[n_parents-1].ch != _T('!') &&
+                   ctx->containers[n_parents-1].ch != _T(':') &&
                    n_brothers + n_children == 0  &&  ctx->current_block == NULL  &&
                    ctx->n_block_bytes > (int) sizeof(MD_BLOCK))
                 {
@@ -6232,7 +6266,8 @@ md_analyze_line(MD_CTX* ctx, OFF beg, OFF* p_end,
         {
             if(pivot_line->type == MD_LINE_TEXT  &&  n_parents == ctx->n_containers  &&
                         (off >= ctx->size || ISNEWLINE(off))  &&  container.ch != _T('>')
-                        && container.ch != _T('!'))
+                        && container.ch != _T('!')
+                        &&  container.ch != _T(':'))
             {
                 /* Noop. List mark followed by a blank line cannot interrupt a paragraph. */
             } else if(pivot_line->type == MD_LINE_TEXT  &&  n_parents == ctx->n_containers  &&
@@ -6440,7 +6475,7 @@ md_analyze_line(MD_CTX* ctx, OFF beg, OFF* p_end,
     /* If we belong to a list after seeing a blank line, the list is loose. */
     if(prev_line_has_list_loosening_effect  &&  line->type != MD_LINE_BLANK  &&  n_parents + n_brothers > 0) {
         MD_CONTAINER* c = &ctx->containers[n_parents + n_brothers - 1];
-        if(c->ch != _T('>') && c->ch != _T('!')) {
+        if(c->ch != _T('>')  &&  c->ch != _T('!')  &&  c->ch != _T(':')) {
             MD_BLOCK* block = (MD_BLOCK*) (((char*)ctx->block_bytes) + c->block_byte_off);
             block->flags |= MD_BLOCK_LOOSE_LIST;
         }
diff --git a/src/md4c.h b/src/md4c.h
index c1b8b3e..b484185 100644
--- a/src/md4c.h
+++ b/src/md4c.h
@@ -61,6 +61,9 @@ typedef enum MD_BLOCKTYPE {
     /* <div class="box">...</div> */
     MD_BLOCK_BOX,
 
+    /* indented block */
+    MD_BLOCK_INDENT,
+
     /* <ul>...</ul>
      * Detail: Structure MD_BLOCK_UL_DETAIL. */
     MD_BLOCK_UL,
@@ -334,6 +337,7 @@ typedef struct MD_SPAN_WIKILINK {
 #define MD_FLAG_BOLD                        0x10000 /* Enable bold extension */
 #define MD_FLAG_BOX                         0x20000 /* Enable box extension */
 #define MD_FLAG_HIGHLIGHT                   0x40000 /* Enable highlight extension */
+#define MD_FLAG_INDENT                      0x80000 /* Enable indent extension */
 
 #define MD_FLAG_PERMISSIVEAUTOLINKS         (MD_FLAG_PERMISSIVEEMAILAUTOLINKS | MD_FLAG_PERMISSIVEURLAUTOLINKS | MD_FLAG_PERMISSIVEWWWAUTOLINKS)
 #define MD_FLAG_NOHTML                      (MD_FLAG_NOHTMLBLOCKS | MD_FLAG_NOHTMLSPANS)