diff --git a/src/ChangeLog b/src/ChangeLog
index 2c55dc037f8..92410490141 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,5 +1,7 @@
 2006-04-08  Eli Zaretskii  <eliz@gnu.org>
 
+	* alloc.c [STDC_HEADERS]: Include stddef.h.
+
 	* lisp.h (PSEUDOVECSIZE): Fix last change.
 
 2006-04-08  Stefan Monnier  <monnier@iro.umontreal.ca>
diff --git a/src/alloc.c b/src/alloc.c
index 5b42a0016a8..1d3dc10c411 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -23,6 +23,10 @@ Boston, MA 02110-1301, USA.  */
 #include <stdio.h>
 #include <limits.h>		/* For CHAR_BIT.  */
 
+#ifdef STDC_HEADERS
+#include <stddef.h>		/* For offsetof, used by PSEUDOVECSIZE. */
+#endif
+
 #ifdef ALLOC_DEBUG
 #undef INLINE
 #endif