diff --git a/src/vim9compile.c b/src/vim9compile.c
index 8a46b2f..dd3eff4 100644
--- a/src/vim9compile.c
+++ b/src/vim9compile.c
@@ -4800,11 +4800,6 @@
 			semsg(_(e_variable_already_declared), name);
 			goto theend;
 		    }
-		    else if (lvar->lv_const)
-		    {
-			semsg(_(e_cannot_assign_to_constant), name);
-			goto theend;
-		    }
 		}
 		else
 		{
@@ -4960,6 +4955,11 @@
 	    semsg(_(e_cannot_assign_to_argument), name);
 	    goto theend;
 	}
+	if (!is_decl && lvar != NULL && lvar->lv_const && !has_index)
+	{
+	    semsg(_(e_cannot_assign_to_constant), name);
+	    goto theend;
+	}
 
 	if (!heredoc)
 	{