diff --git a/configure.ac b/configure.ac
index 043aed5b36..55e6191cfa 100644
--- a/configure.ac
+++ b/configure.ac
@@ -134,12 +134,6 @@ AC_CHECK_HEADERS([sys/personality.h])
 AC_CHECK_HEADERS([linux/fs.h])
 
 
-# Check for tr1/unordered_set.
-AC_LANG_PUSH(C++)
-AC_CHECK_HEADERS([tr1/unordered_set])
-AC_LANG_POP(C++)
-
-
 AC_DEFUN([NEED_PROG],
 [
 AC_PATH_PROG($1, $2)
diff --git a/src/libexpr/symbol-table.hh b/src/libexpr/symbol-table.hh
index 08e31d4965..140662b515 100644
--- a/src/libexpr/symbol-table.hh
+++ b/src/libexpr/symbol-table.hh
@@ -3,10 +3,7 @@
 #include "config.h"
 
 #include <map>
-
-#if HAVE_TR1_UNORDERED_SET
-#include <tr1/unordered_set>
-#endif
+#include <unordered_set>
 
 #include "types.hh"
 
@@ -70,11 +67,7 @@ inline std::ostream & operator << (std::ostream & str, const Symbol & sym)
 class SymbolTable
 {
 private:
-#if HAVE_TR1_UNORDERED_SET
-    typedef std::tr1::unordered_set<string> Symbols;
-#else
-    typedef std::set<string> Symbols;
-#endif
+    typedef std::unordered_set<string> Symbols;
     Symbols symbols;
 
 public:
diff --git a/src/libstore/local-store.hh b/src/libstore/local-store.hh
index 54331e448a..e58e6563f1 100644
--- a/src/libstore/local-store.hh
+++ b/src/libstore/local-store.hh
@@ -1,16 +1,12 @@
 #pragma once
 
 #include <string>
+#include <unordered_set>
 
 #include "store-api.hh"
 #include "util.hh"
 #include "pathlocks.hh"
 
-#if HAVE_TR1_UNORDERED_SET
-#include <tr1/unordered_set>
-#endif
-
-
 
 class sqlite3;
 class sqlite3_stmt;
@@ -306,11 +302,7 @@ private:
 
     void checkDerivationOutputs(const Path & drvPath, const Derivation & drv);
 
-#if HAVE_TR1_UNORDERED_SET
-    typedef std::tr1::unordered_set<ino_t> InodeHash;
-#else
-    typedef std::set<ino_t> InodeHash;
-#endif
+    typedef std::unordered_set<ino_t> InodeHash;
 
     InodeHash loadInodeHash();
     Strings readDirectoryIgnoringInodes(const Path & path, const InodeHash & inodeHash);
diff --git a/src/libstore/local.mk b/src/libstore/local.mk
index 40cb25dc5f..64dbfa3c5b 100644
--- a/src/libstore/local.mk
+++ b/src/libstore/local.mk
@@ -21,8 +21,7 @@ libstore_CXXFLAGS = \
  -DNIX_LOG_DIR=\"$(localstatedir)/log/nix\" \
  -DNIX_CONF_DIR=\"$(sysconfdir)/nix\" \
  -DNIX_LIBEXEC_DIR=\"$(libexecdir)\" \
- -DNIX_BIN_DIR=\"$(bindir)\" \
- -DPACKAGE_VERSION=\"$(PACKAGE_VERSION)\"
+ -DNIX_BIN_DIR=\"$(bindir)\"
 
 $(d)/local-store.cc: $(d)/schema.sql.hh