diff --git a/src/plugins/cppeditor/cppeditor.cpp b/src/plugins/cppeditor/cppeditor.cpp
index 4b861658fc0..ba062d06d3b 100644
--- a/src/plugins/cppeditor/cppeditor.cpp
+++ b/src/plugins/cppeditor/cppeditor.cpp
@@ -521,7 +521,7 @@ sourceLocationsToExtraSelections(const std::vector<SourceLocationContainer> &sou
     const auto textCharFormat = occurrencesTextCharFormat();
 
     QList<QTextEdit::ExtraSelection> selections;
-    selections.reserve(sourceLocations.size());
+    selections.reserve(int(sourceLocations.size()));
 
     auto sourceLocationToExtraSelection = [&] (const SourceLocationContainer &sourceLocation) {
         QTextEdit::ExtraSelection selection;