diff --git a/CHANGES b/CHANGES
index 5efbf45..15fc1d5 100644
--- a/CHANGES
+++ b/CHANGES
@@ -17,7 +17,7 @@ Corrections:
 	Unsetenv() was conditional in sysutils.c but not in xio-openssl.c thus
 	building failed on Solaris 9.
 	Thanks to Greg Earle for reporting this issue and providing a patch.
-	
+
 Porting:
 	In gcc version 10 the default changed from -fcommon to -fno-common.
 	Consequently, linking filan and procan failed with error
@@ -26,6 +26,9 @@ Porting:
 	Debian issue 957823
 	Thanks to László Böszörményi and others for reporting this issue.
 
+	Solaris 9 does not provide strndup(); added substitute code.
+	Thanks to Greg Earle for providing a patch.
+
 Testing:
 	test.sh now produces a list of tests that could not be performed for
 	any reason. This helps to analyse these cases.
diff --git a/compat.h b/compat.h
index d40ccc5..d68adf7 100644
--- a/compat.h
+++ b/compat.h
@@ -704,4 +704,8 @@ typedef int sig_atomic_t;
 extern const char *hstrerror(int);
 #endif
 
+#if !HAVE_PROTOTYPE_LIB_strndup
+extern char *strndup (const char *s, size_t n);
+#endif
+
 #endif /* !defined(__compat_h_included) */
diff --git a/config.h.in b/config.h.in
index 17a6549..7a99c7c 100644
--- a/config.h.in
+++ b/config.h.in
@@ -114,6 +114,9 @@
 /* Define if you have the inet_aton function. */
 #undef HAVE_INET_ATON
 
+/* Define if you have the strndup function. */
+#undef HAVE_PROTOTYPE_LIB_strndup
+
 /* Define if you have the memrchr function. */
 #undef HAVE_PROTOTYPE_LIB_memrchr
 
diff --git a/configure.ac b/configure.ac
index d788dc1..4b0bc09 100644
--- a/configure.ac
+++ b/configure.ac
@@ -777,6 +777,7 @@ AC_CHECK_PROTOTYPE_LIB(strdup)
 AC_CHECK_PROTOTYPE_LIB(strerror)
 AC_CHECK_PROTOTYPE_LIB(strstr)
 AC_CHECK_PROTOTYPE_LIB(getipnodebyname)
+AC_CHECK_PROTOTYPE_LIB(strndup)
 AC_CHECK_PROTOTYPE_LIB(memrchr)
 AC_CHECK_PROTOTYPE_LIB(if_indextoname)
 AC_CHECK_PROTOTYPE_LIB(ptsname)