diff --git a/src/onion/response.c b/src/onion/response.c
index eaaf3cae..6cfbb9e1 100644
--- a/src/onion/response.c
+++ b/src/onion/response.c
@@ -49,7 +49,7 @@ const char *onion_response_code_description(int code);
 
 #ifndef DONT_USE_DATE_HEADER
 static volatile time_t onion_response_last_time = 0;
-static char *onion_response_last_date_header = NULL;
+static char onion_response_last_date_header[128] = { 0 };
 #ifdef HAVE_PTHREADS
 pthread_rwlock_t onion_response_date_lock = PTHREAD_RWLOCK_INITIALIZER;
 #endif
@@ -101,26 +101,33 @@ onion_response *onion_response_new(onion_request * req) {
 
     if (t != current) {
       ONION_DEBUG("Recalculating date header");
-      char current_datetime[200];
+      char current_datetime[sizeof(onion_response_last_date_header)];
 
       if (localtime_r(&t, &tmp) == NULL) {
         perror("localtime");
         exit(EXIT_FAILURE);
       }
 
-      if (strftime
-          (current_datetime, sizeof(current_datetime),
-           "%a, %d %b %Y %H:%M:%S %Z", &tmp) == 0) {
+      size_t len_current_datetime = strftime(
+              current_datetime, sizeof(current_datetime),
+              "%a, %d %b %Y %H:%M:%S %Z", &tmp);
+      if ( len_current_datetime == 0) {
         fprintf(stderr, "strftime returned 0");
         exit(EXIT_FAILURE);
       }
 #ifdef HAVE_PTHREADS
       pthread_rwlock_wrlock(&onion_response_date_lock);
 #endif
-      __sync_bool_compare_and_swap(&onion_response_last_time, current, t);
-      if (onion_response_last_date_header)
-        onion_low_free(onion_response_last_date_header);
-      onion_response_last_date_header = onion_low_strdup(current_datetime);
+      if ( __sync_bool_compare_and_swap(&onion_response_last_time, current, t)){
+          /* First thread with new timestamp updates date_header.
+           * 'current_datetime' of other threads will be ignored.
+           * (… and except very rare conditions, it is the
+           * same string in all threads.)
+           */
+          assert(len_current_datetime < sizeof(onion_response_last_date_header));
+          memcpy(onion_response_last_date_header,
+                  current_datetime, len_current_datetime);
+      }
 #ifdef HAVE_PTHREADS
       pthread_rwlock_unlock(&onion_response_date_lock);
 #endif
@@ -129,7 +136,7 @@ onion_response *onion_response_new(onion_request * req) {
 #ifdef HAVE_PTHREADS
   pthread_rwlock_rdlock(&onion_response_date_lock);
 #endif
-  assert(onion_response_last_date_header);
+  assert(onion_response_last_date_header[0]);
   onion_dict_add(res->headers, "Date", onion_response_last_date_header,
                  OD_DUP_VALUE);
 #ifdef HAVE_PTHREADS