diff --git a/src/libs/qmuparser/qmuparsertest.cpp b/src/libs/qmuparser/qmuparsertest.cpp
index 26c76f117..9f2d928a1 100644
--- a/src/libs/qmuparser/qmuparsertest.cpp
+++ b/src/libs/qmuparser/qmuparsertest.cpp
@@ -80,7 +80,7 @@ int QmuParserTester::IsHexVal ( const QString &a_szExpr, int *a_iPos, qreal *a_f
     Q_UNUSED(locale)
     Q_UNUSED(decimal)
     Q_UNUSED(thousand)
-    if ( a_szExpr.data()[1] == 0 || ( a_szExpr.data()[0] != '0' || a_szExpr.data()[1] != 'x' ) )
+    if ( a_szExpr.size() <= 2 || ( a_szExpr.at(0) != '0' || a_szExpr.at(1) != 'x' ) )
     {
         return 0;
     }
diff --git a/src/libs/qmuparser/qmuparsertokenreader.cpp b/src/libs/qmuparser/qmuparsertokenreader.cpp
index 7545302f5..c3ce39fed 100644
--- a/src/libs/qmuparser/qmuparsertokenreader.cpp
+++ b/src/libs/qmuparser/qmuparsertokenreader.cpp
@@ -221,7 +221,7 @@ QmuParserTokenReader::token_type QmuParserTokenReader::ReadNextToken(const QLoca
     token_type tok;
 
     // Ignore all non printable characters when reading the expression
-    while (m_strFormula.at(m_iPos) > QChar() && m_strFormula.at(m_iPos) <= QChar(0x20))
+    while (m_strFormula.size() > m_iPos && m_strFormula.at(m_iPos) <= QChar(0x20))
     {
         ++m_iPos;
     }