diff --git a/ChangeLog b/ChangeLog
index 4acae97821..559754ec6f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2012-05-10  Joseph Myers  <joseph@codesourcery.com>
+
+	* include/stdc-predef.h (__STDC_NO_THREADS__): Define.
+
 2012-05-10  Maxim Kuvyrkov  <maxim@codesourcery.com>
 	    Joseph Myers  <joseph@codesourcery.com>
 	    Paul Pluzhnikov  <ppluzhnikov@google.com>
diff --git a/include/stdc-predef.h b/include/stdc-predef.h
index ef10c1672e..146bc5c2b5 100644
--- a/include/stdc-predef.h
+++ b/include/stdc-predef.h
@@ -33,4 +33,7 @@
 /* wchar_t uses ISO 10646-1 (2nd ed., published 2000-09-15) / Unicode 3.1.  */
 #define __STDC_ISO_10646__		200009L
 
+/* We do not support C11 <threads.h>.  */
+#define __STDC_NO_THREADS__		1
+
 #endif