diff --git a/src/common/util.c b/src/common/util.c
index 3f3fb8b6a6..11c592ca96 100644
--- a/src/common/util.c
+++ b/src/common/util.c
@@ -838,35 +838,42 @@ write_str_to_file(const char *fname, const char *str, int bin)
 int write_bytes_to_file(const char *fname, const char *str, size_t len,
                         int bin)
 {
-  char tempname[1024];
+  size_t tempname_len;
+  char *tempname;
   int fd;
   int result;
-  if ((strlcpy(tempname,fname,1024) >= 1024) ||
-      (strlcat(tempname,".tmp",1024) >= 1024)) {
-    log(LOG_WARN, "Filename %s.tmp too long (>1024 chars)", fname);
-    return -1;
+  tempname_len = strlen(fname)+16;
+  tor_assert(tempname_len > strlen(fname)); /*check for overflow*/
+  tempname = tor_malloc(tempname_len);
+  if (tor_snprintf(tempname, tempname_len, "%s.tmp", fname)<0) {
+    log(LOG_WARN, "Failed to generate filename");
+    goto err;
   }
   if ((fd = open(tempname, O_WRONLY|O_CREAT|O_TRUNC|(bin?O_BINARY:O_TEXT), 0600))
       < 0) {
     log(LOG_WARN, "Couldn't open %s for writing: %s", tempname,
         strerror(errno));
-    return -1;
+    goto err;
   }
   result = write_all(fd, str, len, 0);
   if (result < 0 || (size_t)result != len) {
     log(LOG_WARN, "Error writing to %s: %s", tempname, strerror(errno));
     close(fd);
-    return -1;
+    goto err;
   }
   if (close(fd)) {
     log(LOG_WARN,"Error flushing to %s: %s", tempname, strerror(errno));
-    return -1;
+    goto err;
   }
   if (replace_file(tempname, fname)) {
     log(LOG_WARN, "Error replacing %s: %s", fname, strerror(errno));
-    return -1;
+    goto err;
   }
+  tor_free(tempname);
   return 0;
+ err:
+  tor_free(tempname);
+  return -1;
 }
 
 /** Read the contents of <b>filename</b> into a newly allocated string; return the
diff --git a/src/or/config.c b/src/or/config.c
index 47b292e465..aeaa538177 100644
--- a/src/or/config.c
+++ b/src/or/config.c
@@ -2307,7 +2307,6 @@ validate_data_directory(or_options_t *options) {
 static int
 write_configuration_file(const char *fname, or_options_t *options)
 {
-  char fn_tmp[1024];
   char *old_val=NULL, *new_val=NULL, *new_conf=NULL;
   int rename_old = 0, r;
   size_t len;
@@ -2340,9 +2339,14 @@ write_configuration_file(const char *fname, or_options_t *options)
 
   if (rename_old) {
     int i = 1;
+    size_t fn_tmp_len = strlen(fname)+32;
+    char *fn_tmp;
+    tor_assert(fn_tmp_len > strlen(fname)); /*check for overflow*/
+    fn_tmp = tor_malloc(fn_tmp_len);
     while (1) {
-      if (tor_snprintf(fn_tmp, sizeof(fn_tmp), "%s.orig.%d", fname, i)<0) {
-        log_fn(LOG_WARN, "Filename too long");
+      if (tor_snprintf(fn_tmp, fn_tmp_len, "%s.orig.%d", fname, i)<0) {
+        log_fn(LOG_WARN, "tor_snprintf failed inexplicably");
+        tor_free(fn_tmp);
         goto err;
       }
       if (file_status(fn_tmp) == FN_NOENT)
@@ -2351,6 +2355,7 @@ write_configuration_file(const char *fname, or_options_t *options)
     }
     log_fn(LOG_NOTICE, "Renaming old configuration file to %s", fn_tmp);
     rename(fname, fn_tmp);
+    tor_free(fn_tmp);
   }
 
   write_str_to_file(fname, new_val, 0);