diff --git a/src/libstore/build/local-derivation-goal.cc b/src/libstore/build/local-derivation-goal.cc
index 220f80602..7e69d4145 100644
--- a/src/libstore/build/local-derivation-goal.cc
+++ b/src/libstore/build/local-derivation-goal.cc
@@ -1933,7 +1933,7 @@ void LocalDerivationGoal::runChild()
                             "can't map '%1%' to '%2%': mismatched impure paths not supported on Darwin",
                             i.first, i.second.source);
 
-                    string path = i.first;
+                    std::string path = i.first;
                     struct stat st;
                     if (lstat(path.c_str(), &st)) {
                         if (i.second.optional && errno == ENOENT)
@@ -1985,7 +1985,7 @@ void LocalDerivationGoal::runChild()
                 args.push_back("IMPORT_DIR=" + settings.nixDataDir + "/nix/sandbox/");
                 if (allowLocalNetworking) {
                     args.push_back("-D");
-                    args.push_back(string("_ALLOW_LOCAL_NETWORKING=1"));
+                    args.push_back(std::string("_ALLOW_LOCAL_NETWORKING=1"));
                 }
                 args.push_back(drv->builder);
             } else {
@@ -2383,14 +2383,10 @@ void LocalDerivationGoal::registerOutputs()
             [&](DerivationOutputCAFloating dof) {
                 return newInfoFromCA(dof);
             },
-                [&](DerivationOutputDeferred) {
+            [&](DerivationOutputDeferred) -> ValidPathInfo {
                 // No derivation should reach that point without having been
                 // rewritten first
                 assert(false);
-                // Ugly, but the compiler insists on having this return a value
-                // of type `ValidPathInfo` despite the `assert(false)`, so
-                // let's provide it
-                return *(ValidPathInfo*)0;
             },
         }, output.output);
 
diff --git a/src/libstore/build/local-derivation-goal.hh b/src/libstore/build/local-derivation-goal.hh
index 2d1222d2f..95692c60d 100644
--- a/src/libstore/build/local-derivation-goal.hh
+++ b/src/libstore/build/local-derivation-goal.hh
@@ -62,7 +62,7 @@ struct LocalDerivationGoal : public DerivationGoal
     Environment env;
 
 #if __APPLE__
-    typedef string SandboxProfile;
+    typedef std::string SandboxProfile;
     SandboxProfile additionalSandboxProfile;
 #endif
 
diff --git a/src/libstore/gc.cc b/src/libstore/gc.cc
index fd38b731c..024da66c1 100644
--- a/src/libstore/gc.cc
+++ b/src/libstore/gc.cc
@@ -413,7 +413,7 @@ void LocalStore::findRuntimeRoots(Roots & roots, bool censor)
         try {
             std::regex lsofRegex(R"(^n(/.*)$)");
             auto lsofLines =
-                tokenizeString<std::vector<string>>(runProgram(LSOF, true, { "-n", "-w", "-F", "n" }), "\n");
+                tokenizeString<std::vector<std::string>>(runProgram(LSOF, true, { "-n", "-w", "-F", "n" }), "\n");
             for (const auto & line : lsofLines) {
                 std::smatch match;
                 if (std::regex_match(line, match, lsofRegex))