diff --git a/src/config.in b/src/config.in
index 0e2e0a2623b..6ebcde54c24 100644
--- a/src/config.in
+++ b/src/config.in
@@ -113,6 +113,8 @@ and this notice must be preserved on all copies.  */
 #undef HAVE_XRMSETDATABASE
 #undef HAVE_RANDOM
 
+#undef HAVE_BCOPY
+
 /* If using GNU, then support inline function declarations. */
 #ifdef __GNUC__
 #define INLINE __inline__
@@ -194,6 +196,13 @@ and this notice must be preserved on all copies.  */
 #define SIGTYPE RETSIGTYPE
 #endif
 
+/* The rest of the code currently tests the CPP symbol BSTRING.
+   Override any claims made by the system-description files.  */
+#undef BSTRING
+#ifdef HAVE_BCOPY
+#define BSTRING
+#endif
+
 /* Non-ANSI C compilers usually don't have volatile.  */
 #ifndef HAVE_VOLATILE
 #ifndef __STDC__