diff --git a/csi.c b/csi.c
index 4be35c60..6fca2c24 100644
--- a/csi.c
+++ b/csi.c
@@ -484,16 +484,16 @@ csi_dispatch(struct terminal *term, uint8_t final)
             break;
         }
 
-        case 'l': {
-            /* Horizontal index */
+        case 'h':
+            /* smir - insert mode enable */
             assert(false && "untested");
-            int param = param_get(term, 0, 1);
-            int col = term->cursor.col;
-
-            col = (col + param * 8) / 8 * 8;
-            term_cursor_right(term, col - term->cursor.col);
+            term->insert_mode = true;
+            break;
+
+        case 'l':
+            /* rmir - insert mode disable */
+            term->insert_mode = false;
             break;
-        }
 
         case 'r': {
             int start = param_get(term, 0, 1);
diff --git a/terminal.h b/terminal.h
index a96b1b70..f48158e5 100644
--- a/terminal.h
+++ b/terminal.h
@@ -131,9 +131,11 @@ struct terminal {
     pid_t slave;
     int ptmx;
 
-    bool hide_cursor;
     enum decckm decckm;
     enum keypad_mode keypad_mode;
+    bool hide_cursor;
+    bool auto_margin;
+    bool insert_mode;
     bool bracketed_paste;
 
     struct vt vt;
diff --git a/vt.c b/vt.c
index c5786b2f..b00b840d 100644
--- a/vt.c
+++ b/vt.c
@@ -701,6 +701,15 @@ action(struct terminal *term, enum action action, uint8_t c)
         struct cell *cell = &term->grid->cur_line[term->cursor.col];
         term_damage_update(term, term->cursor.linear, 1);
 
+        if (term->insert_mode) {
+            assert(false && "untested");
+            grid_memmove(
+                term->grid, term->cursor.linear + 1, term->cursor.linear,
+                term->cols - term->cursor.col - 1);
+            term_damage_update(
+                term, term->cursor.linear + 1, term->cols - term->cursor.col - 1);
+        }
+
         if (term->vt.utf8.idx > 0) {
             //LOG_DBG("print: UTF8: %.*s", (int)term->vt.utf8.idx, term->vt.utf8.data);
             memcpy(cell->c, term->vt.utf8.data, term->vt.utf8.idx);