diff --git a/src/checks/level1/README-qstring-left.md b/src/checks/level1/README-qstring-left.md
index 5e60728..b4b53a9 100644
--- a/src/checks/level1/README-qstring-left.md
+++ b/src/checks/level1/README-qstring-left.md
@@ -1,4 +1,9 @@
 # qstring-left
 
-Finds places where you're using `QString::left(0)` instead of `QString::at(0)`.
-The later form is cheaper.
+Finds places where you're using `QString::left(1)` instead of `QString::at(0)`.
+The later form is cheaper, as it doesn't deep-copy the string.
+
+There's however another difference between the two: `left(1)` will return an empty
+string if the string is empty, while `QString::at(0)` will assert. So be sure
+that the string can't be empty, or add a `if (!str.isEmpty()` guard, which is still
+faster than calling `left()` for the cases which deep-copy.
diff --git a/src/checks/level1/qstring-left.cpp b/src/checks/level1/qstring-left.cpp
index 51d3f82..580d903 100644
--- a/src/checks/level1/qstring-left.cpp
+++ b/src/checks/level1/qstring-left.cpp
@@ -1,64 +1,64 @@
 /*
   This file is part of the clazy static checker.
 
   Copyright (C) 2016 Sergio Martins <smartins@kde.org>
 
   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public
   License as published by the Free Software Foundation; either
   version 2 of the License, or (at your option) any later version.
 
   This library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Library General Public License for more details.
 
   You should have received a copy of the GNU Library General Public License
   along with this library; see the file COPYING.LIB.  If not, write to
   the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
   Boston, MA 02110-1301, USA.
 */
 
 #include "qstring-left.h"
 #include "Utils.h"
 #include "HierarchyUtils.h"
 #include "QtUtils.h"
 #include "TypeUtils.h"
 #include "StringUtils.h"
 #include "checkmanager.h"
 
 #include <clang/AST/AST.h>
 
 using namespace clang;
 using namespace std;
 
 
 QStringLeft::QStringLeft(const std::string &name, const clang::CompilerInstance &ci)
     : CheckBase(name, ci)
 {
 }
 
 
 void QStringLeft::VisitStmt(clang::Stmt *stmt)
 {
     auto memberCall = dyn_cast<CXXMemberCallExpr>(stmt);
     if (!memberCall || StringUtils::qualifiedMethodName(memberCall) != "QString::left")
         return;
 
     if (memberCall->getNumArgs() == 0) // Doesn't happen
         return;
 
     Expr *firstArg = memberCall->getArg(0);
     auto lt = firstArg ? dyn_cast<IntegerLiteral>(firstArg) : nullptr;
     if (lt) {
         const auto value = lt->getValue();
         if (value == 0) {
             emitWarning(stmt, "QString::left(0) returns an empty string");
         } else if (value == 1){
-            emitWarning(stmt, "Use QString::at(0) instead of QString::left(1)");
+            emitWarning(stmt, "Use QString::at(0) instead of QString::left(1) to avoid temporary allocations (just be sure the string isn't empty).");
         }
     }
 }
 
 
 REGISTER_CHECK_WITH_FLAGS("qstring-left", QStringLeft, CheckLevel1)
diff --git a/tests/qstring-left/main.cpp.expected b/tests/qstring-left/main.cpp.expected
index b1ae352..f46ff9d 100644
--- a/tests/qstring-left/main.cpp.expected
+++ b/tests/qstring-left/main.cpp.expected
@@ -1,2 +1,2 @@
 qstring-left/main.cpp:6:14: warning: QString::left(0) returns an empty string [-Wclazy-qstring-left]
-qstring-left/main.cpp:7:9: warning: Use QString::at(0) instead of QString::left(1) [-Wclazy-qstring-left]
+qstring-left/main.cpp:7:9: warning: Use QString::at(0) instead of QString::left(1) to avoid temporary allocations (just be sure the string isn't empty). [-Wclazy-qstring-left]