diff --git a/config-linuxmodule.h.in b/config-linuxmodule.h.in
index 9c50fcd742..511d9c0cc7 100644
--- a/config-linuxmodule.h.in
+++ b/config-linuxmodule.h.in
@@ -115,6 +115,9 @@
 /* Define if you have the skb_recycle function. */
 #undef HAVE_SKB_RECYCLE
 
+/* Define if you have the strnlen function. */
+#define HAVE_STRNLEN 1
+
 /* Define to 1 if Linux defines the type 'uintptr_t'. */
 #undef HAVE_UINTPTR_T_LINUXMODULE
 
diff --git a/config-userlevel.h.in b/config-userlevel.h.in
index b71565a18b..2396c3147e 100644
--- a/config-userlevel.h.in
+++ b/config-userlevel.h.in
@@ -132,6 +132,9 @@
 /* Define if you have the <strings.h> header file. */
 #undef HAVE_STRINGS_H
 
+/* Define if you have the strnlen function. */
+#undef HAVE_STRNLEN
+
 /* Define if you have the strtoul function. */
 #undef HAVE_STRTOUL
 
diff --git a/configure b/configure
index 55544ad2e3..2b07e1adb3 100755
--- a/configure
+++ b/configure
@@ -6473,7 +6473,7 @@ fi
 done
 
 
-for ac_func in random snprintf strtoul tcgetpgrp vsnprintf
+for ac_func in random snprintf strnlen strtoul tcgetpgrp vsnprintf
 do :
   as_ac_var=`$as_echo "ac_cv_func_$ac_func" | $as_tr_sh`
 ac_fn_c_check_func "$LINENO" "$ac_func" "$as_ac_var"
diff --git a/configure.in b/configure.in
index 63b7e132d3..ec366335e7 100644
--- a/configure.in
+++ b/configure.in
@@ -407,7 +407,7 @@ dnl
 
 AC_LANG_C
 AC_REPLACE_FUNCS(strerror)
-AC_CHECK_FUNCS(random snprintf strtoul tcgetpgrp vsnprintf)
+AC_CHECK_FUNCS(random snprintf strnlen strtoul tcgetpgrp vsnprintf)
 AC_LANG_CPLUSPLUS
 
 
diff --git a/lib/error.cc b/lib/error.cc
index 7616873746..b56823b760 100644
--- a/lib/error.cc
+++ b/lib/error.cc
@@ -487,8 +487,13 @@ ErrorHandler::vxformat(int default_flags, const char *s, va_list val)
 	    if (flags & cf_alternate_form) {
 		strstore = String(s1).printable();
 		len = strstore.length();
-	    } else
-		len = strlen(s1);
+	    } else {
+#if HAVE_STRNLEN
+		len = (precision >= 0 ? strnlen(s, precision) : strlen(s));
+#else
+		len = strlen(s1); // XXX might touch uninitialized memory
+#endif
+	    }
 
 	    // adjust length for precision
 	    if (precision >= 0 && precision < len)