diff --git a/src/nvim/eval/vars.c b/src/nvim/eval/vars.c
index fc993150a5..7d59f5e872 100644
--- a/src/nvim/eval/vars.c
+++ b/src/nvim/eval/vars.c
@@ -3246,7 +3246,7 @@ static Object opt_from_tv(typval_T *tv, OptIndex opt_idx, const char *option, bo
       const char *strval = tv_get_string_buf_chk(tv, nbuf);
       err = strval == NULL;
       value = CSTR_TO_OBJ(strval);
-    } else if (!is_tty_opt) {
+    } else {
       err = true;
       emsg(_(e_string_required));
     }
diff --git a/test/functional/vimscript/let_spec.lua b/test/functional/vimscript/let_spec.lua
index 1cd12f42d1..54153db049 100644
--- a/test/functional/vimscript/let_spec.lua
+++ b/test/functional/vimscript/let_spec.lua
@@ -114,6 +114,15 @@ describe(':let', function()
     command('let &equalalways %= 1')
     eq(false, api.nvim_get_option_value('equalalways', {}))
   end)
+
+  it('assigning bool/special to a string option gives E928, not a crash', function()
+    for _, v in ipairs({ 'v:true', 'v:false', 'v:null' }) do
+      -- Regular string option.
+      eq('Vim(let):E928: String required', t.pcall_err(command, 'let &makeprg = ' .. v))
+      -- TTY option ("t_" pseudo-option).
+      eq('Vim(let):E928: String required', t.pcall_err(command, 'let &t_Co = ' .. v))
+    end
+  end)
 end)
 
 describe(':let and :const', function()