diff --git a/configure.ac b/configure.ac
--- a/configure.ac
+++ b/configure.ac
@@ -1320,6 +1320,7 @@
 AC_CHECK_SIZEOF(unsigned int)
 AC_CHECK_SIZEOF(unsigned long)
 AC_CHECK_SIZEOF(unsigned long long)
+AC_CHECK_SIZEOF(void *)
 AC_HEADER_TIME
 AC_CHECK_SIZEOF(time_t,,[[
 #include <stdio.h>
diff --git a/tests/gpgscm/scheme-private.h b/tests/gpgscm/scheme-private.h
--- a/tests/gpgscm/scheme-private.h
+++ b/tests/gpgscm/scheme-private.h
@@ -42,6 +42,11 @@
 
 /* cell structure */
 struct cell {
+#if defined(BIG_ENDIAN_HOST) && defined(SIZEOF_UNSIGNED_INT) \
+    && defined(SIZEOF_VOID_P) \
+    && (SIZEOF_VOID_P > SIZEOF_UNSIGNED_INT)
+  unsigned int _padding;
+#endif
   unsigned int _flag;
   union {
     struct {