diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 9fe38789..a314e01e 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -81,7 +81,7 @@ public:
 
     /* The allowed filesystem paths in restricted or pure evaluation
        mode. */
-    std::experimental::optional<PathSet> allowedPaths;
+    std::optional<PathSet> allowedPaths;
 
     Value vEmptySet;
 
diff --git a/src/libexpr/get-drvs.cc b/src/libexpr/get-drvs.cc
index d38ed2df..21a4d791 100644
--- a/src/libexpr/get-drvs.cc
+++ b/src/libexpr/get-drvs.cc
@@ -295,7 +295,7 @@ static bool getDerivation(EvalState & state, Value & v,
 }
 
 
-std::experimental::optional<DrvInfo> getDerivation(EvalState & state, Value & v,
+std::optional<DrvInfo> getDerivation(EvalState & state, Value & v,
     bool ignoreAssertionFailures)
 {
     Done done;
diff --git a/src/libexpr/get-drvs.hh b/src/libexpr/get-drvs.hh
index daaa635f..d7860fc6 100644
--- a/src/libexpr/get-drvs.hh
+++ b/src/libexpr/get-drvs.hh
@@ -78,7 +78,7 @@ typedef list<DrvInfo> DrvInfos;
 
 /* If value `v' denotes a derivation, return a DrvInfo object
    describing it. Otherwise return nothing. */
-std::experimental::optional<DrvInfo> getDerivation(EvalState & state,
+std::optional<DrvInfo> getDerivation(EvalState & state,
     Value & v, bool ignoreAssertionFailures);
 
 void getDerivations(EvalState & state, Value & v, const string & pathPrefix,
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 0da9f702..6b0c55e7 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -555,7 +555,7 @@ static void prim_derivationStrict(EvalState & state, const Pos & pos, Value * *
 
     PathSet context;
 
-    std::experimental::optional<std::string> outputHash;
+    std::optional<std::string> outputHash;
     std::string outputHashAlgo;
     bool outputHashRecursive = false;
 
diff --git a/src/libexpr/primops/fetchGit.cc b/src/libexpr/primops/fetchGit.cc
index b46d2f25..aaf02c85 100644
--- a/src/libexpr/primops/fetchGit.cc
+++ b/src/libexpr/primops/fetchGit.cc
@@ -26,7 +26,7 @@ struct GitInfo
 std::regex revRegex("^[0-9a-fA-F]{40}$");
 
 GitInfo exportGit(ref<Store> store, const std::string & uri,
-    std::experimental::optional<std::string> ref, std::string rev,
+    std::optional<std::string> ref, std::string rev,
     const std::string & name)
 {
     if (evalSettings.pureEval && rev == "")
@@ -190,7 +190,7 @@ GitInfo exportGit(ref<Store> store, const std::string & uri,
 static void prim_fetchGit(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
     std::string url;
-    std::experimental::optional<std::string> ref;
+    std::optional<std::string> ref;
     std::string rev;
     std::string name = "source";
     PathSet context;
diff --git a/src/libstore/build.cc b/src/libstore/build.cc
index 47ee8b48..6b88b130 100644
--- a/src/libstore/build.cc
+++ b/src/libstore/build.cc
@@ -2413,7 +2413,7 @@ void DerivationGoal::writeStructuredAttrs()
        objects consisting entirely of those values. (So nested
        arrays or objects are not supported.) */
 
-    auto handleSimpleType = [](const nlohmann::json & value) -> std::experimental::optional<std::string> {
+    auto handleSimpleType = [](const nlohmann::json & value) -> std::optional<std::string> {
         if (value.is_string())
             return shellEscape(value);
 
@@ -3311,8 +3311,8 @@ void DerivationGoal::checkOutputs(const std::map<Path, ValidPathInfo> & outputs)
         struct Checks
         {
             bool ignoreSelfRefs = false;
-            std::experimental::optional<uint64_t> maxSize, maxClosureSize;
-            std::experimental::optional<Strings> allowedReferences, allowedRequisites, disallowedReferences, disallowedRequisites;
+            std::optional<uint64_t> maxSize, maxClosureSize;
+            std::optional<Strings> allowedReferences, allowedRequisites, disallowedReferences, disallowedRequisites;
         };
 
         /* Compute the closure and closure size of some output. This
@@ -3359,7 +3359,7 @@ void DerivationGoal::checkOutputs(const std::map<Path, ValidPathInfo> & outputs)
                         info.path, closureSize, *checks.maxClosureSize);
             }
 
-            auto checkRefs = [&](const std::experimental::optional<Strings> & value, bool allowed, bool recursive)
+            auto checkRefs = [&](const std::optional<Strings> & value, bool allowed, bool recursive)
             {
                 if (!value) return;
 
@@ -3413,7 +3413,7 @@ void DerivationGoal::checkOutputs(const std::map<Path, ValidPathInfo> & outputs)
                     if (maxClosureSize != output->end())
                         checks.maxClosureSize = maxClosureSize->get<uint64_t>();
 
-                    auto get = [&](const std::string & name) -> std::experimental::optional<Strings> {
+                    auto get = [&](const std::string & name) -> std::optional<Strings> {
                         auto i = output->find(name);
                         if (i != output->end()) {
                             Strings res;
diff --git a/src/libstore/parsed-derivations.cc b/src/libstore/parsed-derivations.cc
index dc328648..17fde00a 100644
--- a/src/libstore/parsed-derivations.cc
+++ b/src/libstore/parsed-derivations.cc
@@ -16,7 +16,7 @@ ParsedDerivation::ParsedDerivation(const Path & drvPath, BasicDerivation & drv)
     }
 }
 
-std::experimental::optional<std::string> ParsedDerivation::getStringAttr(const std::string & name) const
+std::optional<std::string> ParsedDerivation::getStringAttr(const std::string & name) const
 {
     if (structuredAttrs) {
         auto i = structuredAttrs->find(name);
@@ -56,7 +56,7 @@ bool ParsedDerivation::getBoolAttr(const std::string & name, bool def) const
     }
 }
 
-std::experimental::optional<Strings> ParsedDerivation::getStringsAttr(const std::string & name) const
+std::optional<Strings> ParsedDerivation::getStringsAttr(const std::string & name) const
 {
     if (structuredAttrs) {
         auto i = structuredAttrs->find(name);
diff --git a/src/libstore/parsed-derivations.hh b/src/libstore/parsed-derivations.hh
index 0a82c146..ed07dc65 100644
--- a/src/libstore/parsed-derivations.hh
+++ b/src/libstore/parsed-derivations.hh
@@ -8,22 +8,22 @@ class ParsedDerivation
 {
     Path drvPath;
     BasicDerivation & drv;
-    std::experimental::optional<nlohmann::json> structuredAttrs;
+    std::optional<nlohmann::json> structuredAttrs;
 
 public:
 
     ParsedDerivation(const Path & drvPath, BasicDerivation & drv);
 
-    const std::experimental::optional<nlohmann::json> & getStructuredAttrs() const
+    const std::optional<nlohmann::json> & getStructuredAttrs() const
     {
         return structuredAttrs;
     }
 
-    std::experimental::optional<std::string> getStringAttr(const std::string & name) const;
+    std::optional<std::string> getStringAttr(const std::string & name) const;
 
     bool getBoolAttr(const std::string & name, bool def = false) const;
 
-    std::experimental::optional<Strings> getStringsAttr(const std::string & name) const;
+    std::optional<Strings> getStringsAttr(const std::string & name) const;
 
     StringSet getRequiredSystemFeatures() const;
 
diff --git a/src/libstore/remote-store.hh b/src/libstore/remote-store.hh
index e5ab79e5..80f18ab7 100644
--- a/src/libstore/remote-store.hh
+++ b/src/libstore/remote-store.hh
@@ -149,7 +149,7 @@ public:
 private:
 
     ref<RemoteStore::Connection> openConnection() override;
-    std::experimental::optional<std::string> path;
+    std::optional<std::string> path;
 };
 
 
diff --git a/src/libutil/lru-cache.hh b/src/libutil/lru-cache.hh
index 9b8290e6..8b83f842 100644
--- a/src/libutil/lru-cache.hh
+++ b/src/libutil/lru-cache.hh
@@ -2,7 +2,7 @@
 
 #include <map>
 #include <list>
-#include <experimental/optional>
+#include <optional>
 
 namespace nix {
 
@@ -64,7 +64,7 @@ public:
 
     /* Look up an item in the cache. If it exists, it becomes the most
        recently used item. */
-    std::experimental::optional<Value> get(const Key & key)
+    std::optional<Value> get(const Key & key)
     {
         auto i = data.find(key);
         if (i == data.end()) return {};
diff --git a/src/libutil/serialise.cc b/src/libutil/serialise.cc
index 0e75eeec..8201549f 100644
--- a/src/libutil/serialise.cc
+++ b/src/libutil/serialise.cc
@@ -171,7 +171,7 @@ std::unique_ptr<Source> sinkToSource(
 
         std::function<void(Sink &)> fun;
         std::function<void()> eof;
-        std::experimental::optional<coro_t::pull_type> coro;
+        std::optional<coro_t::pull_type> coro;
         bool started = false;
 
         SinkToSource(std::function<void(Sink &)> fun, std::function<void()> eof)
diff --git a/src/libutil/util.cc b/src/libutil/util.cc
index 7eca3557..e3dcd246 100644
--- a/src/libutil/util.cc
+++ b/src/libutil/util.cc
@@ -965,7 +965,7 @@ std::vector<char *> stringsToCharPtrs(const Strings & ss)
 
 
 string runProgram(Path program, bool searchPath, const Strings & args,
-    const std::experimental::optional<std::string> & input)
+    const std::optional<std::string> & input)
 {
     RunOptions opts(program, args);
     opts.searchPath = searchPath;
diff --git a/src/libutil/util.hh b/src/libutil/util.hh
index bda87bee..9f239bff 100644
--- a/src/libutil/util.hh
+++ b/src/libutil/util.hh
@@ -14,7 +14,7 @@
 #include <cstdio>
 #include <map>
 #include <sstream>
-#include <experimental/optional>
+#include <optional>
 #include <future>
 
 #ifndef HAVE_STRUCT_DIRENT_D_TYPE
@@ -259,14 +259,14 @@ pid_t startProcess(std::function<void()> fun, const ProcessOptions & options = P
    shell backtick operator). */
 string runProgram(Path program, bool searchPath = false,
     const Strings & args = Strings(),
-    const std::experimental::optional<std::string> & input = {});
+    const std::optional<std::string> & input = {});
 
 struct RunOptions
 {
     Path program;
     bool searchPath = true;
     Strings args;
-    std::experimental::optional<std::string> input;
+    std::optional<std::string> input;
     Source * standardIn = nullptr;
     Sink * standardOut = nullptr;
     bool _killStderr = false;
diff --git a/src/nix/add-to-store.cc b/src/nix/add-to-store.cc
index d0003790..e86b96e3 100644
--- a/src/nix/add-to-store.cc
+++ b/src/nix/add-to-store.cc
@@ -8,7 +8,7 @@ using namespace nix;
 struct CmdAddToStore : MixDryRun, StoreCommand
 {
     Path path;
-    std::experimental::optional<std::string> namePart;
+    std::optional<std::string> namePart;
 
     CmdAddToStore()
     {