diff --git a/ChangeLog b/ChangeLog
index b1b25c60ec..dd5a2b5b18 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2015-11-16  Florian Weimer  <fweimer@redhat.com>
+
+	* math/test-signgam-finite-c99.c (_Mlong_double_): Undefine.
+
 2015-11-14  H.J. Lu  <hongjiu.lu@intel.com>
 
 	* config.make.in (have-glob-dat-reloc): New.
diff --git a/math/test-signgam-finite-c99.c b/math/test-signgam-finite-c99.c
index fd9cdd37dc..bd3bdca661 100644
--- a/math/test-signgam-finite-c99.c
+++ b/math/test-signgam-finite-c99.c
@@ -18,6 +18,7 @@
 
 #undef _LIBC
 #undef _GNU_SOURCE
+#undef _Mlong_double_
 #define _ISOMAC
 
 #include <math.h>