diff --git a/ChangeLog b/ChangeLog
index f61a292d97..7368be4c78 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2018-11-06  Gabriel F. T. Gomes  <gabriel@inconstante.eti.br>
+
+	* misc/Makefile (tests): Add tst-ldbl-warn.
+	* misc/tst-ldbl-warn.c: New file.
+
 2018-11-06  Gabriel F. T. Gomes  <gabriel@inconstante.eti.br>
 
 	* argp/Makefile (tests): Add tst-ldbl-argp.
diff --git a/misc/Makefile b/misc/Makefile
index 30e0673c8a..201de124f4 100644
--- a/misc/Makefile
+++ b/misc/Makefile
@@ -84,7 +84,8 @@ tests := tst-dirname tst-tsearch tst-fdset tst-efgcvt tst-mntent tst-hsearch \
 	 tst-error1 tst-pselect tst-insremque tst-mntent2 bug-hsearch1 \
 	 tst-mntent-blank-corrupt tst-mntent-blank-passno bug18240 \
 	 tst-preadvwritev tst-preadvwritev64 tst-makedev tst-empty \
-	 tst-preadvwritev2 tst-preadvwritev64v2 tst-warn-wide
+	 tst-preadvwritev2 tst-preadvwritev64v2 tst-warn-wide \
+	 tst-ldbl-warn
 
 # Tests which need libdl.
 ifeq (yes,$(build-shared))
diff --git a/misc/tst-ldbl-warn.c b/misc/tst-ldbl-warn.c
new file mode 100644
index 0000000000..3ac0e4c873
--- /dev/null
+++ b/misc/tst-ldbl-warn.c
@@ -0,0 +1,120 @@
+/* Test for the long double conversions in *warn* functions.
+   Copyright (C) 2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <err.h>
+#include <errno.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <support/check.h>
+#include <support/xmemstream.h>
+
+enum {WARN, WARNX, VWARN, VWARNX};
+
+static void
+do_one_test (int select, const char *format, va_list args,
+	     long double arg1, double arg2, long double arg3,
+	     double arg4, const char *expected)
+{
+  /* Prepare in-memory buffer to hold the output.  */
+  struct xmemstream stream;
+  xopen_memstream (&stream);
+  FILE *old_stderr = stderr;
+  stderr = stream.out;
+
+  /* Write to the buffer using one of the *warn* functions.  */
+  errno = 0;
+  switch (select)
+    {
+      case WARN:
+	warn (format, arg1, arg2, arg3, arg4);
+	break;
+      case WARNX:
+	warnx (format, arg1, arg2, arg3, arg4);
+	break;
+      case VWARN:
+	vwarn (format, args);
+	break;
+      case VWARNX:
+	vwarnx (format, args);
+	break;
+    }
+
+  stderr = old_stderr;
+
+  /* Close the in-memory stream and check the output buffer.  */
+  xfclose_memstream (&stream);
+  if (strcmp (stream.buffer, expected) != 0)
+    FAIL_EXIT1 ("error:\n"
+		"    expected: '%s'\n"
+		"      actual: '%s'\n",
+		expected, stream.buffer);
+
+  if (stream.buffer != NULL)
+    free (stream.buffer);
+}
+
+static void
+do_test_call_varg (const char *format, ...)
+{
+  va_list args;
+
+  va_start (args, format);
+  do_one_test (VWARN, format, args, 0, 0, 0, 0,
+	       "tst-ldbl-warn: "
+	       "-1.000000 - -2.000000 - -3.000000 - -4.000000: Success\n");
+  va_end (args);
+
+  va_start (args, format);
+  do_one_test (VWARNX, format, args, 0, 0, 0, 0,
+	       "tst-ldbl-warn: "
+	       "-1.000000 - -2.000000 - -3.000000 - -4.000000\n");
+  va_end (args);
+}
+
+static void
+do_test_call_rarg (const char *format, long double arg1, double arg2,
+		   long double arg3, double arg4)
+{
+  va_list args;
+  memset (&args, 0, sizeof (args));
+  do_one_test (WARN, format, args, arg1, arg2, arg3, arg4,
+	       "tst-ldbl-warn: "
+	       "-1.000000 - -2.000000 - -3.000000 - -4.000000: Success\n");
+  do_one_test (WARNX, format, args, arg1, arg2, arg3, arg4,
+	       "tst-ldbl-warn: "
+	       "-1.000000 - -2.000000 - -3.000000 - -4.000000\n");
+}
+
+static int
+do_test (void)
+{
+  long double arg1 = -1;
+  long double arg3 = -3;
+  double arg2 = -2;
+  double arg4 = -4;
+
+  do_test_call_rarg ("%Lf - %f - %Lf - %f", arg1, arg2, arg3, arg4);
+  do_test_call_varg ("%Lf - %f - %Lf - %f", arg1, arg2, arg3, arg4);
+
+  return 0;
+}
+
+#include <support/test-driver.c>