diff --git a/src/compat/endian.h b/src/compat/endian.h
index 6e3e795c1..a67f3a14c 100644
--- a/src/compat/endian.h
+++ b/src/compat/endian.h
@@ -1,172 +1,217 @@
 // Copyright (c) 2014-2016 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #ifndef BITCOIN_COMPAT_ENDIAN_H
 #define BITCOIN_COMPAT_ENDIAN_H
 
 #if defined(HAVE_CONFIG_H)
 #include <config/bitcoin-config.h>
 #endif
 
 #include <compat/byteswap.h>
 
 #include <cstdint>
 
 #if defined(HAVE_ENDIAN_H)
 #include <endian.h>
 #elif defined(HAVE_SYS_ENDIAN_H)
 #include <sys/endian.h>
 #endif
 
+#ifndef HAVE_CONFIG_H
+// While not technically a supported configuration, defaulting to defining these
+// DECLs when we were compiled without autotools makes it easier for other build
+// systems to build things like libbitcoinconsensus for strange targets.
+#ifdef htobe16
+#define HAVE_DECL_HTOBE16 1
+#endif
+#ifdef htole16
+#define HAVE_DECL_HTOLE16 1
+#endif
+#ifdef be16toh
+#define HAVE_DECL_BE16TOH 1
+#endif
+#ifdef le16toh
+#define HAVE_DECL_LE16TOH 1
+#endif
+
+#ifdef htobe32
+#define HAVE_DECL_HTOBE32 1
+#endif
+#ifdef htole32
+#define HAVE_DECL_HTOLE32 1
+#endif
+#ifdef be32toh
+#define HAVE_DECL_BE32TOH 1
+#endif
+#ifdef le32toh
+#define HAVE_DECL_LE32TOH 1
+#endif
+
+#ifdef htobe64
+#define HAVE_DECL_HTOBE64 1
+#endif
+#ifdef htole64
+#define HAVE_DECL_HTOLE64 1
+#endif
+#ifdef be64toh
+#define HAVE_DECL_BE64TOH 1
+#endif
+#ifdef le64toh
+#define HAVE_DECL_LE64TOH 1
+#endif
+
+#endif // HAVE_CONFIG_H
+
 #if defined(WORDS_BIGENDIAN)
 
 #if HAVE_DECL_HTOBE16 == 0
 inline uint16_t htobe16(uint16_t host_16bits) {
     return host_16bits;
 }
 #endif // HAVE_DECL_HTOBE16
 
 #if HAVE_DECL_HTOLE16 == 0
 inline uint16_t htole16(uint16_t host_16bits) {
     return bswap_16(host_16bits);
 }
 #endif // HAVE_DECL_HTOLE16
 
 #if HAVE_DECL_BE16TOH == 0
 inline uint16_t be16toh(uint16_t big_endian_16bits) {
     return big_endian_16bits;
 }
 #endif // HAVE_DECL_BE16TOH
 
 #if HAVE_DECL_LE16TOH == 0
 inline uint16_t le16toh(uint16_t little_endian_16bits) {
     return bswap_16(little_endian_16bits);
 }
 #endif // HAVE_DECL_LE16TOH
 
 #if HAVE_DECL_HTOBE32 == 0
 inline uint32_t htobe32(uint32_t host_32bits) {
     return host_32bits;
 }
 #endif // HAVE_DECL_HTOBE32
 
 #if HAVE_DECL_HTOLE32 == 0
 inline uint32_t htole32(uint32_t host_32bits) {
     return bswap_32(host_32bits);
 }
 #endif // HAVE_DECL_HTOLE32
 
 #if HAVE_DECL_BE32TOH == 0
 inline uint32_t be32toh(uint32_t big_endian_32bits) {
     return big_endian_32bits;
 }
 #endif // HAVE_DECL_BE32TOH
 
 #if HAVE_DECL_LE32TOH == 0
 inline uint32_t le32toh(uint32_t little_endian_32bits) {
     return bswap_32(little_endian_32bits);
 }
 #endif // HAVE_DECL_LE32TOH
 
 #if HAVE_DECL_HTOBE64 == 0
 inline uint64_t htobe64(uint64_t host_64bits) {
     return host_64bits;
 }
 #endif // HAVE_DECL_HTOBE64
 
 #if HAVE_DECL_HTOLE64 == 0
 inline uint64_t htole64(uint64_t host_64bits) {
     return bswap_64(host_64bits);
 }
 #endif // HAVE_DECL_HTOLE64
 
 #if HAVE_DECL_BE64TOH == 0
 inline uint64_t be64toh(uint64_t big_endian_64bits) {
     return big_endian_64bits;
 }
 #endif // HAVE_DECL_BE64TOH
 
 #if HAVE_DECL_LE64TOH == 0
 inline uint64_t le64toh(uint64_t little_endian_64bits) {
     return bswap_64(little_endian_64bits);
 }
 #endif // HAVE_DECL_LE64TOH
 
 #else // WORDS_BIGENDIAN
 
 #if HAVE_DECL_HTOBE16 == 0
 inline uint16_t htobe16(uint16_t host_16bits) {
     return bswap_16(host_16bits);
 }
 #endif // HAVE_DECL_HTOBE16
 
 #if HAVE_DECL_HTOLE16 == 0
 inline uint16_t htole16(uint16_t host_16bits) {
     return host_16bits;
 }
 #endif // HAVE_DECL_HTOLE16
 
 #if HAVE_DECL_BE16TOH == 0
 inline uint16_t be16toh(uint16_t big_endian_16bits) {
     return bswap_16(big_endian_16bits);
 }
 #endif // HAVE_DECL_BE16TOH
 
 #if HAVE_DECL_LE16TOH == 0
 inline uint16_t le16toh(uint16_t little_endian_16bits) {
     return little_endian_16bits;
 }
 #endif // HAVE_DECL_LE16TOH
 
 #if HAVE_DECL_HTOBE32 == 0
 inline uint32_t htobe32(uint32_t host_32bits) {
     return bswap_32(host_32bits);
 }
 #endif // HAVE_DECL_HTOBE32
 
 #if HAVE_DECL_HTOLE32 == 0
 inline uint32_t htole32(uint32_t host_32bits) {
     return host_32bits;
 }
 #endif // HAVE_DECL_HTOLE32
 
 #if HAVE_DECL_BE32TOH == 0
 inline uint32_t be32toh(uint32_t big_endian_32bits) {
     return bswap_32(big_endian_32bits);
 }
 #endif // HAVE_DECL_BE32TOH
 
 #if HAVE_DECL_LE32TOH == 0
 inline uint32_t le32toh(uint32_t little_endian_32bits) {
     return little_endian_32bits;
 }
 #endif // HAVE_DECL_LE32TOH
 
 #if HAVE_DECL_HTOBE64 == 0
 inline uint64_t htobe64(uint64_t host_64bits) {
     return bswap_64(host_64bits);
 }
 #endif // HAVE_DECL_HTOBE64
 
 #if HAVE_DECL_HTOLE64 == 0
 inline uint64_t htole64(uint64_t host_64bits) {
     return host_64bits;
 }
 #endif // HAVE_DECL_HTOLE64
 
 #if HAVE_DECL_BE64TOH == 0
 inline uint64_t be64toh(uint64_t big_endian_64bits) {
     return bswap_64(big_endian_64bits);
 }
 #endif // HAVE_DECL_BE64TOH
 
 #if HAVE_DECL_LE64TOH == 0
 inline uint64_t le64toh(uint64_t little_endian_64bits) {
     return little_endian_64bits;
 }
 #endif // HAVE_DECL_LE64TOH
 
 #endif // WORDS_BIGENDIAN
 
 #endif // BITCOIN_COMPAT_ENDIAN_H