diff --git a/g10/sign.c b/g10/sign.c
index 2f48a7..c156d4 100644
--- a/g10/sign.c
+++ b/g10/sign.c
@@ -852,8 +852,15 @@ write_signature_packets (ctrl_t ctrl,
       sig->pubkey_algo = pk->pubkey_algo;
       if (timestamp)
         sig->timestamp = timestamp;
-      else
-        sig->timestamp = make_timestamp();
+      else {
+        const char* sig_date;
+        sig_date = getenv("GPG_SIGNATURE_TIMESTAMP");
+        if (sig_date != NULL && *sig_date != '\0') {
+          sig->timestamp = atol(sig_date);
+        } else {
+          sig->timestamp = make_timestamp();
+        }
+      }
       if (duration)
         sig->expiredate = sig->timestamp + duration;
       sig->sig_class = sigclass;