diff --git a/src/libs/3rdparty/cplusplus/TranslationUnit.cpp b/src/libs/3rdparty/cplusplus/TranslationUnit.cpp
index 848f61285cb..e680ee2660e 100644
--- a/src/libs/3rdparty/cplusplus/TranslationUnit.cpp
+++ b/src/libs/3rdparty/cplusplus/TranslationUnit.cpp
@@ -27,6 +27,7 @@
 #include "Literals.h"
 #include "DiagnosticClient.h"
 
+#include "cppassert.h"
 #include <utils/textutils.h>
 
 #include <stack>
@@ -87,6 +88,7 @@ int TranslationUnit::sourceLength() const
 
 void TranslationUnit::setSource(const char *source, int size)
 {
+    CPP_CHECK(source);
     _firstSourceChar = source;
     _lastSourceChar = source + size;
 }
diff --git a/src/libs/cplusplus/CppDocument.cpp b/src/libs/cplusplus/CppDocument.cpp
index 6dc59bf1bf1..c7454589aa7 100644
--- a/src/libs/cplusplus/CppDocument.cpp
+++ b/src/libs/cplusplus/CppDocument.cpp
@@ -527,7 +527,7 @@ Document::Ptr Document::create(const FilePath &filePath)
 void Document::setUtf8Source(const QByteArray &source)
 {
     _source = source;
-    _translationUnit->setSource(_source.constBegin(), _source.size());
+    _translationUnit->setSource(_source.constData(), _source.size());
 }
 
 LanguageFeatures Document::languageFeatures() const