diff --git a/src/libexpr/symbol-table.hh b/src/libexpr/symbol-table.hh
index a090ebae5..48d20c29d 100644
--- a/src/libexpr/symbol-table.hh
+++ b/src/libexpr/symbol-table.hh
@@ -17,8 +17,8 @@ namespace nix {
 class Symbol
 {
 private:
-    const string * s; // pointer into SymbolTable
-    Symbol(const string * s) : s(s) { };
+    const std::string * s; // pointer into SymbolTable
+    Symbol(const std::string * s) : s(s) { };
     friend class SymbolTable;
 
 public:
@@ -72,7 +72,7 @@ class SymbolTable
 {
 private:
     std::unordered_map<std::string_view, Symbol> symbols;
-    std::list<string> store;
+    std::list<std::string> store;
 
 public:
     Symbol create(std::string_view s)
@@ -84,7 +84,7 @@ public:
         auto it = symbols.find(s);
         if (it != symbols.end()) return it->second;
 
-        const string & rawSym = store.emplace_back(s);
+        auto & rawSym = store.emplace_back(s);
         return symbols.emplace(rawSym, Symbol(&rawSym)).first->second;
     }
 
diff --git a/src/libexpr/value.hh b/src/libexpr/value.hh
index bef5cd6bd..3fdff71a5 100644
--- a/src/libexpr/value.hh
+++ b/src/libexpr/value.hh
@@ -77,20 +77,20 @@ class ExternalValueBase
 
     public:
     /* Return a simple string describing the type */
-    virtual string showType() const = 0;
+    virtual std::string showType() const = 0;
 
     /* Return a string to be used in builtins.typeOf */
-    virtual string typeOf() const = 0;
+    virtual std::string typeOf() const = 0;
 
     /* Coerce the value to a string. Defaults to uncoercable, i.e. throws an
-     * error
+     * error.
      */
-    virtual string coerceToString(const Pos & pos, PathSet & context, bool copyMore, bool copyToStore) const;
+    virtual std::string coerceToString(const Pos & pos, PathSet & context, bool copyMore, bool copyToStore) const;
 
     /* Compare to another value of the same type. Defaults to uncomparable,
      * i.e. always false.
      */
-    virtual bool operator==(const ExternalValueBase & b) const;
+    virtual bool operator ==(const ExternalValueBase & b) const;
 
     /* Print the value as JSON. Defaults to unconvertable, i.e. throws an error */
     virtual void printValueAsJSON(EvalState & state, bool strict,
diff --git a/src/libstore/machines.hh b/src/libstore/machines.hh
index 341d9bd97..834626de9 100644
--- a/src/libstore/machines.hh
+++ b/src/libstore/machines.hh
@@ -8,19 +8,19 @@ class Store;
 
 struct Machine {
 
-    const string storeUri;
-    const std::vector<string> systemTypes;
-    const string sshKey;
+    const std::string storeUri;
+    const std::vector<std::string> systemTypes;
+    const std::string sshKey;
     const unsigned int maxJobs;
     const unsigned int speedFactor;
-    const std::set<string> supportedFeatures;
-    const std::set<string> mandatoryFeatures;
+    const std::set<std::string> supportedFeatures;
+    const std::set<std::string> mandatoryFeatures;
     const std::string sshPublicHostKey;
     bool enabled = true;
 
-    bool allSupported(const std::set<string> & features) const;
+    bool allSupported(const std::set<std::string> & features) const;
 
-    bool mandatoryMet(const std::set<string> & features) const;
+    bool mandatoryMet(const std::set<std::string> & features) const;
 
     Machine(decltype(storeUri) storeUri,
         decltype(systemTypes) systemTypes,
diff --git a/src/libstore/names.hh b/src/libstore/names.hh
index ecbad10b3..3977fc6cc 100644
--- a/src/libstore/names.hh
+++ b/src/libstore/names.hh
@@ -10,9 +10,9 @@ struct Regex;
 
 struct DrvName
 {
-    string fullName;
-    string name;
-    string version;
+    std::string fullName;
+    std::string name;
+    std::string version;
     unsigned int hits;
 
     DrvName();
diff --git a/src/libutil/types.hh b/src/libutil/types.hh
index a26c9a966..bea2673ca 100644
--- a/src/libutil/types.hh
+++ b/src/libutil/types.hh
@@ -11,20 +11,17 @@
 
 namespace nix {
 
-using std::string;
-
-typedef std::list<string> Strings;
-typedef std::set<string> StringSet;
-typedef std::map<string, string> StringMap;
+typedef std::list<std::string> Strings;
+typedef std::set<std::string> StringSet;
+typedef std::map<std::string, std::string> StringMap;
 
 /* Paths are just strings. */
-
-typedef string Path;
+typedef std::string Path;
 typedef std::string_view PathView;
 typedef std::list<Path> Paths;
 typedef std::set<Path> PathSet;
 
-typedef std::vector<std::pair<string, string>> Headers;
+typedef std::vector<std::pair<std::string, std::string>> Headers;
 
 /* Helper class to run code at startup. */
 template<typename T>