diff --git a/ChangeLog b/ChangeLog
index 2a65383f12..be9ed44d83 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,9 @@
 2017-11-24  Joseph Myers  <joseph@codesourcery.com>
 
+	* stdlib/tst-strtod-round-skeleton.c
+	(__STDC_WANT_IEC_60559_TYPES_EXT__): Define before including
+	headers.
+
 	* math/gen-tgmath-tests.py (Type.init_types): Pass suffix argument
 	for combinations of long double with _Float64 and _Float64x.
 
diff --git a/stdlib/tst-strtod-round-skeleton.c b/stdlib/tst-strtod-round-skeleton.c
index 763c9ce983..05d8a4c303 100644
--- a/stdlib/tst-strtod-round-skeleton.c
+++ b/stdlib/tst-strtod-round-skeleton.c
@@ -20,6 +20,7 @@
 /* Defining _LIBC_TEST ensures long double math functions are
    declared in the headers.  */
 #define _LIBC_TEST 1
+#define __STDC_WANT_IEC_60559_TYPES_EXT__
 #include <fenv.h>
 #include <float.h>
 #include <math.h>