diff --git a/build_msvc/bitcoin_config.h.in b/build_msvc/bitcoin_config.h.in
index e25024e871..b37d536947 100644
--- a/build_msvc/bitcoin_config.h.in
+++ b/build_msvc/bitcoin_config.h.in
@@ -125,10 +125,6 @@
    don't. */
 #define HAVE_DECL_STRERROR_R 0
 
-/* Define to 1 if you have the declaration of `strnlen', and to 0 if you
-   don't. */
-#define HAVE_DECL_STRNLEN 1
-
 /* Define if the dllexport attribute is supported. */
 #define HAVE_DLLEXPORT_ATTRIBUTE 1
 
diff --git a/configure.ac b/configure.ac
index d051b48908..d349e0f0ba 100644
--- a/configure.ac
+++ b/configure.ac
@@ -984,7 +984,6 @@ AC_CHECK_DECLS([getifaddrs, freeifaddrs],[CHECK_SOCKET],,
     [#include <sys/types.h>
     #include <ifaddrs.h>]
 )
-AC_CHECK_DECLS([strnlen])
 
 dnl These are used for daemonization in bitcoind
 AC_CHECK_DECLS([fork])
diff --git a/src/Makefile.am b/src/Makefile.am
index af6bcaf4d7..d3ae9a8d8c 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -606,7 +606,6 @@ libbitcoin_util_a_SOURCES = \
   chainparamsbase.cpp \
   clientversion.cpp \
   compat/glibcxx_sanity.cpp \
-  compat/strnlen.cpp \
   fs.cpp \
   interfaces/echo.cpp \
   interfaces/handler.cpp \
diff --git a/src/compat.h b/src/compat.h
index 237b881b11..3ec4ab53fd 100644
--- a/src/compat.h
+++ b/src/compat.h
@@ -80,10 +80,6 @@ typedef int32_t ssize_t;
 #endif
 #endif
 
-#if HAVE_DECL_STRNLEN == 0
-size_t strnlen( const char *start, size_t max_len);
-#endif // HAVE_DECL_STRNLEN
-
 #ifndef WIN32
 typedef void* sockopt_arg_type;
 #else
diff --git a/src/compat/strnlen.cpp b/src/compat/strnlen.cpp
deleted file mode 100644
index 93a034a664..0000000000
--- a/src/compat/strnlen.cpp
+++ /dev/null
@@ -1,18 +0,0 @@
-// Copyright (c) 2009-2018 The Bitcoin Core developers
-// Distributed under the MIT software license, see the accompanying
-// file COPYING or http://www.opensource.org/licenses/mit-license.php.
-
-#if defined(HAVE_CONFIG_H)
-#include <config/bitcoin-config.h>
-#endif
-
-#include <cstring>
-
-#if HAVE_DECL_STRNLEN == 0
-size_t strnlen( const char *start, size_t max_len)
-{
-    const char *end = (const char *)memchr(start, '\0', max_len);
-
-    return end ? (size_t)(end - start) : max_len;
-}
-#endif // HAVE_DECL_STRNLEN