diff --git a/libctf/ChangeLog b/libctf/ChangeLog
index 0be82801845..642ed3f83c1 100644
--- a/libctf/ChangeLog
+++ b/libctf/ChangeLog
@@ -1,3 +1,7 @@
+2020-07-22  Nick Alcock  <nick.alcock@oracle.com>
+
+	* ctf-impl.h [!__GNUC__] (__extension__): Define to nothing.
+
 2020-07-22  Nick Alcock  <nick.alcock@oracle.com>
 
 	* ctf-archive.c (ctf_archive_count): New.
diff --git a/libctf/ctf-impl.h b/libctf/ctf-impl.h
index 4661aa8c7a9..f832c71b97c 100644
--- a/libctf/ctf-impl.h
+++ b/libctf/ctf-impl.h
@@ -65,6 +65,7 @@ extern "C"
 #define _libctf_unlikely_(x) (x)
 #define _libctf_unused_
 #define _libctf_malloc_
+#define __extension__
 
 #endif