diff --git a/openbsd-compat/bsd-asprintf.c b/openbsd-compat/bsd-asprintf.c
index 3368195d4..7b83448ca 100644
--- a/openbsd-compat/bsd-asprintf.c
+++ b/openbsd-compat/bsd-asprintf.c
@@ -25,18 +25,6 @@
 #include <stdarg.h>
 #include <stdlib.h>
 
-#ifndef VA_COPY
-# ifdef HAVE_VA_COPY
-#  define VA_COPY(dest, src) va_copy(dest, src)
-# else
-#  ifdef HAVE___VA_COPY
-#   define VA_COPY(dest, src) __va_copy(dest, src)
-#  else
-#   define VA_COPY(dest, src) (dest) = (src)
-#  endif
-# endif
-#endif
-
 #define INIT_SZ	128
 
 int
diff --git a/openbsd-compat/bsd-snprintf.c b/openbsd-compat/bsd-snprintf.c
index 23a635989..d95b6a401 100644
--- a/openbsd-compat/bsd-snprintf.c
+++ b/openbsd-compat/bsd-snprintf.c
@@ -99,18 +99,6 @@
 # undef HAVE_VSNPRINTF
 #endif
 
-#ifndef VA_COPY
-# ifdef HAVE_VA_COPY
-#  define VA_COPY(dest, src) va_copy(dest, src)
-# else
-#  ifdef HAVE___VA_COPY
-#   define VA_COPY(dest, src) __va_copy(dest, src)
-#  else
-#   define VA_COPY(dest, src) (dest) = (src)
-#  endif
-# endif
-#endif
-
 #if !defined(HAVE_SNPRINTF) || !defined(HAVE_VSNPRINTF)
 
 #include <ctype.h>
diff --git a/openbsd-compat/openbsd-compat.h b/openbsd-compat/openbsd-compat.h
index 997541e43..37d2064cd 100644
--- a/openbsd-compat/openbsd-compat.h
+++ b/openbsd-compat/openbsd-compat.h
@@ -253,6 +253,23 @@ int mbtowc(wchar_t *, const char*, size_t);
 # include <stdarg.h>
 #endif
 
+/*
+ * Some platforms unconditionally undefine va_copy() so we define VA_COPY()
+ * instead.  This is known to be the case on at least some configurations of
+ * AIX with the xlc compiler.
+ */
+#ifndef VA_COPY
+# ifdef HAVE_VA_COPY
+#  define VA_COPY(dest, src) va_copy(dest, src)
+# else
+#  ifdef HAVE___VA_COPY
+#   define VA_COPY(dest, src) __va_copy(dest, src)
+#  else
+#   define VA_COPY(dest, src) (dest) = (src)
+#  endif
+# endif
+#endif
+
 #ifndef HAVE_VASPRINTF
 int vasprintf(char **, const char *, va_list);
 #endif
diff --git a/sshbuf-getput-basic.c b/sshbuf-getput-basic.c
index ad21ae574..74c49be7c 100644
--- a/sshbuf-getput-basic.c
+++ b/sshbuf-getput-basic.c
@@ -270,7 +270,7 @@ sshbuf_putfv(struct sshbuf *buf, const char *fmt, va_list ap)
 	int r, len;
 	u_char *p;
 
-	va_copy(ap2, ap);
+	VA_COPY(ap2, ap);
 	if ((len = vsnprintf(NULL, 0, fmt, ap2)) < 0) {
 		r = SSH_ERR_INVALID_ARGUMENT;
 		goto out;
@@ -280,7 +280,7 @@ sshbuf_putfv(struct sshbuf *buf, const char *fmt, va_list ap)
 		goto out; /* Nothing to do */
 	}
 	va_end(ap2);
-	va_copy(ap2, ap);
+	VA_COPY(ap2, ap);
 	if ((r = sshbuf_reserve(buf, (size_t)len + 1, &p)) < 0)
 		goto out;
 	if ((r = vsnprintf((char *)p, len + 1, fmt, ap2)) != len) {