diff --git a/lldb/source/Symbol/Variable.cpp b/lldb/source/Symbol/Variable.cpp
--- a/lldb/source/Symbol/Variable.cpp
+++ b/lldb/source/Symbol/Variable.cpp
@@ -380,9 +380,8 @@
     llvm::SmallVector<llvm::StringRef, 2> matches;
     variable_list.Clear();
     if (!g_regex.Execute(variable_expr_path, &matches)) {
-      error.SetErrorStringWithFormat(
-          "unable to extract a variable name from '%s'",
-          variable_expr_path.str().c_str());
+      error.SetErrorStringWithFormatv(
+          "unable to extract a variable name from '{0}'", variable_expr_path);
       return error;
     }
     std::string variable_name = matches[1].str();
@@ -411,10 +410,9 @@
         valobj_sp = variable_valobj_sp->GetValueForExpressionPath(
             variable_sub_expr_path);
         if (!valobj_sp) {
-          error.SetErrorStringWithFormat(
-              "invalid expression path '%s' for variable '%s'",
-              variable_sub_expr_path.str().c_str(),
-              var_sp->GetName().GetCString());
+          error.SetErrorStringWithFormatv(
+              "invalid expression path '{0}' for variable '{1}'",
+              variable_sub_expr_path, var_sp->GetName().GetCString());
           variable_list.RemoveVariableAtIndex(i);
           continue;
         }