diff --git a/ChangeLog b/ChangeLog
index 5edd30bbc..cf55aa6c3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2018-01-07  Werner Lemberg  <wl@gnu.org>
+
+	Add check for librt, needed for `ftbench' (#52824).
+
+	* builds/unix/configure.raw (LIB_CLOCK_GETTIME): Define; this will
+	hold `-lrt' if necessary.
+
+	* builds/unix/unix-cc.in (LIB_CLOCK_GETTIME): New variable.
+
 2018-01-07  Ewald Hew  <ewaldhew@gmail.com>
 
 	[psaux] Fix Type 1 glyphs with too many stem hints.
diff --git a/builds/unix/configure.raw b/builds/unix/configure.raw
index 126e0914b..b5d11b2fb 100644
--- a/builds/unix/configure.raw
+++ b/builds/unix/configure.raw
@@ -509,6 +509,21 @@ if test x"$with_harfbuzz" = xyes -a "$have_harfbuzz" = no; then
 fi
 
 
+# check for librt
+#
+# We need `clock_gettime' for the `ftbench' demo program.
+#
+# The code is modeled after gnulib's file `clock_time.m4', ignoring
+# very old Solaris systems.
+
+LIB_CLOCK_GETTIME=
+AC_SEARCH_LIBS([clock_gettime],
+               [rt],
+               [test "$ac_cv_search_clock_gettime" = "none required" \
+                || LIB_CLOCK_GETTIME=$ac_cv_search_clock_gettime])
+AC_SUBST([LIB_CLOCK_GETTIME])
+
+
 # Some options handling SDKs/archs in CFLAGS should be copied
 # to LDFLAGS. Apple TechNote 2137 recommends to include these
 # options in CFLAGS but not in LDFLAGS.
diff --git a/builds/unix/unix-cc.in b/builds/unix/unix-cc.in
index 9b888c7d4..a06246d63 100644
--- a/builds/unix/unix-cc.in
+++ b/builds/unix/unix-cc.in
@@ -93,7 +93,8 @@ CC    := $(LIBTOOL) --mode=compile $(CCraw)
 
 # Linker flags.
 #
-LDFLAGS := @LDFLAGS@
+LDFLAGS           := @LDFLAGS@
+LIB_CLOCK_GETTIME := @LIB_CLOCK_GETTIME@  # for ftbench
 
 
 # export symbols