diff --git a/doc/build-helpers/images/dockertools.section.md b/doc/build-helpers/images/dockertools.section.md
index c1a9526466cd..26c1d9c14a26 100644
--- a/doc/build-helpers/images/dockertools.section.md
+++ b/doc/build-helpers/images/dockertools.section.md
@@ -516,7 +516,7 @@ This allows the function to produce reproducible images.
 `created` (String; _optional_)
 
 : Specifies the time of creation of the generated image.
-  This date will be used for the image metadata, and as the default value for `mtime`.
+  This date will be used for the image metadata.
   This should be either a date and time formatted according to [ISO-8601](https://en.wikipedia.org/wiki/ISO_8601) or `"now"`, in which case the current date will be used.
 
   :::{.caution}
@@ -535,7 +535,7 @@ This allows the function to produce reproducible images.
   Using `"now"` also means that the generated image will not be reproducible anymore (because the date will always change whenever it's built).
   :::
 
-  _Default value:_ the same value as `created`.
+  _Default value:_ `"1970-01-01T00:00:01Z"`.
 
 `uid` (Number; _optional_) []{#dockerTools-buildLayeredImage-arg-uid}
 `gid` (Number; _optional_) []{#dockerTools-buildLayeredImage-arg-gid}
diff --git a/pkgs/build-support/docker/default.nix b/pkgs/build-support/docker/default.nix
index 264cfbf82eed..c19df2937539 100644
--- a/pkgs/build-support/docker/default.nix
+++ b/pkgs/build-support/docker/default.nix
@@ -907,7 +907,7 @@ rec {
     , config ? { }
     , architecture ? defaultArchitecture
     , created ? "1970-01-01T00:00:01Z"
-    , mtime ? created
+    , mtime ? "1970-01-01T00:00:01Z"
     , uid ? 0
     , gid ? 0
     , uname ? "root"