diff --git a/src/libcmd/installables.cc b/src/libcmd/installables.cc
index f9d6d8ce8..227bb64ed 100644
--- a/src/libcmd/installables.cc
+++ b/src/libcmd/installables.cc
@@ -857,6 +857,7 @@ std::vector<FlakeRef> RawInstallablesCommand::getFlakeRefsForCompletion()
 {
     applyDefaultInstallables(rawInstallables);
     std::vector<FlakeRef> res;
+    res.reserve(rawInstallables.size());
     for (auto i : rawInstallables)
         res.push_back(parseFlakeRefWithFragment(
             fetchSettings,
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 84aa6bac9..45d9f86ac 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -91,6 +91,7 @@ StringMap EvalState::realiseContext(const NixStringContext & context, StorePathS
 
     /* Build/substitute the context. */
     std::vector<DerivedPath> buildReqs;
+    buildReqs.reserve(drvs.size());
     for (auto & d : drvs) buildReqs.emplace_back(DerivedPath { d });
     buildStore->buildPaths(buildReqs, bmNormal, store);
 
diff --git a/src/libstore/build/entry-points.cc b/src/libstore/build/entry-points.cc
index 4c1373bfa..3bf22320e 100644
--- a/src/libstore/build/entry-points.cc
+++ b/src/libstore/build/entry-points.cc
@@ -66,6 +66,7 @@ std::vector<KeyedBuildResult> Store::buildPathsWithResults(
     worker.run(goals);
 
     std::vector<KeyedBuildResult> results;
+    results.reserve(state.size());
 
     for (auto & [req, goalPtr] : state)
         results.emplace_back(KeyedBuildResult {
diff --git a/src/libstore/path-with-outputs.cc b/src/libstore/path-with-outputs.cc
index 161d023d1..e526b1ff6 100644
--- a/src/libstore/path-with-outputs.cc
+++ b/src/libstore/path-with-outputs.cc
@@ -37,6 +37,7 @@ DerivedPath StorePathWithOutputs::toDerivedPath() const
 std::vector<DerivedPath> toDerivedPaths(const std::vector<StorePathWithOutputs> ss)
 {
     std::vector<DerivedPath> reqs;
+    reqs.reserve(ss.size());
     for (auto & s : ss) reqs.push_back(s.toDerivedPath());
     return reqs;
 }
diff --git a/src/libutil/executable-path.cc b/src/libutil/executable-path.cc
index 9fb5214b2..e75e147b5 100644
--- a/src/libutil/executable-path.cc
+++ b/src/libutil/executable-path.cc
@@ -56,6 +56,7 @@ ExecutablePath ExecutablePath::parse(const OsString & path)
 OsString ExecutablePath::render() const
 {
     std::vector<PathViewNG> path2;
+    path2.reserve(directories.size());
     for (auto & p : directories)
         path2.push_back(p.native());
     return basicConcatStringsSep(path_var_separator, path2);
diff --git a/src/nix/develop.cc b/src/nix/develop.cc
index c7a733025..9a95bc695 100644
--- a/src/nix/develop.cc
+++ b/src/nix/develop.cc
@@ -610,6 +610,7 @@ struct CmdDevelop : Common, MixEnvironment
 
         else if (!command.empty()) {
             std::vector<std::string> args;
+            args.reserve(command.size());
             for (auto s : command)
                 args.push_back(shellEscape(s));
             script += fmt("exec %s\n", concatStringsSep(" ", args));