diff --git a/src/gui/image/qiconloader.cpp b/src/gui/image/qiconloader.cpp
index 9c09c02c0c..88f505cc39 100644
--- a/src/gui/image/qiconloader.cpp
+++ b/src/gui/image/qiconloader.cpp
@@ -564,9 +564,11 @@ void QIconLoaderEngine::virtual_hook(int id, void *data)
             QIconEngine::AvailableSizesArgument &arg
                     = *reinterpret_cast<QIconEngine::AvailableSizesArgument*>(data);
             arg.sizes.clear();
+            const int N = m_entries.size();
+            arg.sizes.reserve(N);
 
             // Gets all sizes from the DirectoryInfo entries
-            for (int i = 0 ; i < m_entries.size() ; ++i) {
+            for (int i = 0; i < N; ++i) {
                 int size = m_entries.at(i)->dir.size;
                 arg.sizes.append(QSize(size, size));
             }