diff --git a/src/akonadi/akonadistoragesettings.cpp b/src/akonadi/akonadistoragesettings.cpp
--- a/src/akonadi/akonadistoragesettings.cpp
+++ b/src/akonadi/akonadistoragesettings.cpp
@@ -44,6 +44,7 @@
     KConfigGroup config(KSharedConfig::openConfig(), "General");
     QList<Collection::Id> ids = config.readEntry("activeCollections", QList<Collection::Id>());
     Collection::List list;
+    list.reserve(ids.size());
     foreach (const auto &id, ids) {
         list << Collection(id);
     }
diff --git a/src/presentation/contextpagemodel.cpp b/src/presentation/contextpagemodel.cpp
--- a/src/presentation/contextpagemodel.cpp
+++ b/src/presentation/contextpagemodel.cpp
@@ -190,6 +190,7 @@
             return Q_NULLPTR;
 
         auto draggedArtifacts = Domain::Artifact::List();
+        draggedArtifacts.reserve(tasks.size());
         foreach (const Domain::Task::Ptr &task, tasks) {
             draggedArtifacts.append(task.objectCast<Domain::Artifact>());
         }
diff --git a/src/presentation/projectpagemodel.cpp b/src/presentation/projectpagemodel.cpp
--- a/src/presentation/projectpagemodel.cpp
+++ b/src/presentation/projectpagemodel.cpp
@@ -175,6 +175,7 @@
             return Q_NULLPTR;
 
         auto draggedArtifacts = Domain::Artifact::List();
+        draggedArtifacts.reserve(tasks.size());
         foreach (const Domain::Task::Ptr &task, tasks) {
             draggedArtifacts.append(task.objectCast<Domain::Artifact>());
         }
diff --git a/src/presentation/taskinboxpagemodel.cpp b/src/presentation/taskinboxpagemodel.cpp
--- a/src/presentation/taskinboxpagemodel.cpp
+++ b/src/presentation/taskinboxpagemodel.cpp
@@ -159,6 +159,7 @@
             return Q_NULLPTR;
 
         auto draggedArtifacts = Domain::Artifact::List();
+        draggedArtifacts.reserve(tasks.size());
         foreach (const Domain::Task::Ptr &task, tasks) {
             draggedArtifacts.append(task.objectCast<Domain::Artifact>());
         }
diff --git a/tests/testlib/akonadistoragetestbase.cpp b/tests/testlib/akonadistoragetestbase.cpp
--- a/tests/testlib/akonadistoragetestbase.cpp
+++ b/tests/testlib/akonadistoragetestbase.cpp
@@ -159,6 +159,7 @@
     // THEN
     auto collections = job->collections();
     QStringList collectionNames;
+    collectionNames.reserve(collections.size());
     foreach (const auto &collection, collections) {
         collectionNames << collection.name();
     }
@@ -216,6 +217,7 @@
     // THEN
     auto items = job->items();
     QStringList itemRemoteIds;
+    itemRemoteIds.reserve(items.size());
     foreach (const auto &item, items) {
         itemRemoteIds << item.remoteId();
         QVERIFY(item.loadedPayloadParts().contains(Akonadi::Item::FullPayload));
@@ -260,6 +262,7 @@
     // THEN
     auto tags = job->tags();
     QStringList tagGids;
+    tagGids.reserve(tags.size());
     foreach (const auto &tag, tags) {
         tagGids << tag.gid();
         QVERIFY(!tag.name().isEmpty());
@@ -286,6 +289,7 @@
     // THEN
     auto items = job->items();
     QStringList itemRemoteIds;
+    itemRemoteIds.reserve(items.size());
     foreach (const auto &item, items) {
         itemRemoteIds << item.remoteId();
 
diff --git a/tests/units/akonadi/akonadistoragesettingstest.cpp b/tests/units/akonadi/akonadistoragesettingstest.cpp
--- a/tests/units/akonadi/akonadistoragesettingstest.cpp
+++ b/tests/units/akonadi/akonadistoragesettingstest.cpp
@@ -53,6 +53,7 @@
     QList<Akonadi::Collection::Id> idList(int max)
     {
         QList<Akonadi::Collection::Id> list;
+        list.reserve(max);
         for (int i = 1; i < max; i++) {
             list << i;
         }
@@ -62,6 +63,7 @@
     Akonadi::Collection::List colList(int max)
     {
         Akonadi::Collection::List list;
+        list.reserve(max);
         foreach (auto id, idList(max)) {
             list << Collection(id);
         }
diff --git a/tests/units/presentation/artifactfilterproxymodeltest.cpp b/tests/units/presentation/artifactfilterproxymodeltest.cpp
--- a/tests/units/presentation/artifactfilterproxymodeltest.cpp
+++ b/tests/units/presentation/artifactfilterproxymodeltest.cpp
@@ -241,6 +241,7 @@
         output.setSortOrder(Qt::SortOrder(sortOrder));
 
         QStringList outputTitles;
+        outputTitles.reserve(output.rowCount());
         for (int row = 0; row < output.rowCount(); row++) {
             outputTitles << output.index(row, 0).data().toString();
         }
diff --git a/tests/units/presentation/querytreemodeltest.cpp b/tests/units/presentation/querytreemodeltest.cpp
--- a/tests/units/presentation/querytreemodeltest.cpp
+++ b/tests/units/presentation/querytreemodeltest.cpp
@@ -57,6 +57,7 @@
         const QList<bool> doneStates = {true, false, false};
         Q_ASSERT(titles.size() == doneStates.size());
 
+        result.reserve(titles.size());
         for (int i = 0; i < titles.size(); i++) {
             auto task = Domain::Task::Ptr::create();
             task->setTitle(titles.at(i));
@@ -75,6 +76,7 @@
         const QList<bool> doneStates = {true, false, false};
         Q_ASSERT(titles.size() == doneStates.size());
 
+        result.reserve(titles.size());
         for (int i = 0; i < titles.size(); i++) {
             auto task = Domain::Task::Ptr::create();
             task->setTitle(titles.at(i));
diff --git a/tests/units/presentation/tasklistmodeltest.cpp b/tests/units/presentation/tasklistmodeltest.cpp
--- a/tests/units/presentation/tasklistmodeltest.cpp
+++ b/tests/units/presentation/tasklistmodeltest.cpp
@@ -52,6 +52,7 @@
         const QList<bool> doneStates = {true, false, false};
         Q_ASSERT(titles.size() == doneStates.size());
 
+        result.reserve(titles.size());
         for (int i = 0; i < titles.size(); i++) {
             auto task = Domain::Task::Ptr::create();
             task->setTitle(titles.at(i));