diff --git a/src/eval.c b/src/eval.c
index 3cd73b6..b835af8 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -2079,7 +2079,10 @@
 	    }
 	    /* existing variable, need to check if it can be changed */
 	    else if (var_check_ro(lp->ll_di->di_flags, name, FALSE))
+	    {
+		clear_tv(&var1);
 		return NULL;
+	    }
 
 	    if (len == -1)
 		clear_tv(&var1);
diff --git a/src/testdir/test_unlet.vim b/src/testdir/test_unlet.vim
index 4c58785..c20b0be 100644
--- a/src/testdir/test_unlet.vim
+++ b/src/testdir/test_unlet.vim
@@ -17,3 +17,7 @@
   unlet! does_not_exist
   call assert_fails('unlet does_not_exist', 'E108:')
 endfunc
+
+func Test_unlet_fails()
+  call assert_fails('unlet v:["count"]', 'E46:')
+endfunc
diff --git a/src/version.c b/src/version.c
index 5db4b11..7214854 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    344,
+/**/
     343,
 /**/
     342,