diff --git a/configure.ac b/configure.ac
index e1b7281c30..2445b72683 100644
--- a/configure.ac
+++ b/configure.ac
@@ -777,6 +777,39 @@ fi
 
 AC_CHECK_HEADERS([endian.h sys/endian.h byteswap.h stdio.h stdlib.h unistd.h strings.h sys/types.h sys/stat.h sys/select.h sys/prctl.h])
 
+# FD_ZERO may be dependent on a declaration of memcpy, e.g. in SmartOS
+# check that it fails to build without memcpy, then that it builds with
+AC_MSG_CHECKING(FD_ZERO memcpy dependence)
+AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
+    #include <cstddef>
+    #if HAVE_SYS_SELECT_H
+    #include <sys/select.h>
+    #endif
+  ]],[[
+    #if HAVE_SYS_SELECT_H
+    fd_set fds;
+    FD_ZERO(&fds);
+    #endif
+  ]])],
+  [ AC_MSG_RESULT(no) ],
+  [
+      AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
+          #include <cstring>
+          #if HAVE_SYS_SELECT_H
+          #include <sys/select.h>
+          #endif
+        ]], [[
+          #if HAVE_SYS_SELECT_H
+          fd_set fds;
+          FD_ZERO(&fds);
+          #endif
+        ]])],
+        [ AC_MSG_RESULT(yes); AC_DEFINE(HAVE_CSTRING_DEPENDENT_FD_ZERO, 1, [Define this symbol if FD_ZERO is dependent of a memcpy declaration being available]) ],
+        [ AC_MSG_ERROR(failed with cstring include) ]
+      )
+  ]
+)
+
 AC_CHECK_DECLS([getifaddrs, freeifaddrs],,,
     [#include <sys/types.h>
     #include <ifaddrs.h>]
diff --git a/src/Makefile.am b/src/Makefile.am
index 8fc7f61d4b..1ef62a656d 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -484,6 +484,7 @@ libbitcoin_util_a_SOURCES = \
   support/lockedpool.cpp \
   chainparamsbase.cpp \
   clientversion.cpp \
+  compat/glibc_sanity_fdelt.cpp \
   compat/glibc_sanity.cpp \
   compat/glibcxx_sanity.cpp \
   compat/strnlen.cpp \
diff --git a/src/compat/glibc_sanity.cpp b/src/compat/glibc_sanity.cpp
index 1ef66e27b4..cc74f28899 100644
--- a/src/compat/glibc_sanity.cpp
+++ b/src/compat/glibc_sanity.cpp
@@ -1,4 +1,4 @@
-// Copyright (c) 2009-2018 The Bitcoin Core developers
+// Copyright (c) 2009-2019 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
@@ -9,7 +9,7 @@
 #include <cstddef>
 
 #if defined(HAVE_SYS_SELECT_H)
-#include <sys/select.h>
+bool sanity_test_fdelt();
 #endif
 
 extern "C" void* memcpy(void* a, const void* b, size_t c);
@@ -41,21 +41,6 @@ bool sanity_test_memcpy()
     }
     return true;
 }
-
-#if defined(HAVE_SYS_SELECT_H)
-// trigger: Call FD_SET to trigger __fdelt_chk. FORTIFY_SOURCE must be defined
-//   as >0 and optimizations must be set to at least -O2.
-// test: Add a file descriptor to an empty fd_set. Verify that it has been
-//   correctly added.
-bool sanity_test_fdelt()
-{
-    fd_set fds;
-    FD_ZERO(&fds);
-    FD_SET(0, &fds);
-    return FD_ISSET(0, &fds);
-}
-#endif
-
 } // namespace
 
 bool glibc_sanity_test()
diff --git a/src/compat/glibc_sanity_fdelt.cpp b/src/compat/glibc_sanity_fdelt.cpp
new file mode 100644
index 0000000000..87140d0c71
--- /dev/null
+++ b/src/compat/glibc_sanity_fdelt.cpp
@@ -0,0 +1,26 @@
+// Copyright (c) 2009-2019 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
+
+#if defined(HAVE_SYS_SELECT_H)
+#ifdef HAVE_CSTRING_DEPENDENT_FD_ZERO
+#include <cstring>
+#endif
+#include <sys/select.h>
+
+// trigger: Call FD_SET to trigger __fdelt_chk. FORTIFY_SOURCE must be defined
+//   as >0 and optimizations must be set to at least -O2.
+// test: Add a file descriptor to an empty fd_set. Verify that it has been
+//   correctly added.
+bool sanity_test_fdelt()
+{
+    fd_set fds;
+    FD_ZERO(&fds);
+    FD_SET(0, &fds);
+    return FD_ISSET(0, &fds);
+}
+#endif