diff --git a/master_changes.md b/master_changes.md
index ed0ff667171..9c4975018f5 100644
--- a/master_changes.md
+++ b/master_changes.md
@@ -33,6 +33,7 @@ users)
   * Make fetching an archive from cache add missing symlinks [#6068 @kit-ty-kate - fix #6064]
   * [BUG] Fix `opam install --deps-only` set direct dependencies as root packages [#6125 @rjbou]
   * [BUG] Fix `opam install --check pkg` when pkg depends on a non-existing package [#6121 @kit-ty-kate]
+  * Disable shallow clone by default except for opam repositories [#6146 @kit-ty-kate - fix #6145]
 
 ## Build (package)
   * ◈ Add `--verbose-on` option to enable verbose mode on specified package names [#5682 @desumn @rjbou]
@@ -195,6 +196,7 @@ users)
 
 ## opam-repository
  * `OpamRepository.fetch_from_cache`: when an archive is found, add a symlink (or copy) for the ones found in opam file but not in cache [#6068 @kit-ty-kate]
+ * `?full_fetch` is now `true` by default instead of `false` [#6146 @kit-ty-kate - fix #6145]
 
 ## opam-state
  * `OpamStateConfig.opamroot_with_provenance`: restore previous behaviour to `OpamStateConfig.opamroot` for compatibility with third party code [#6047 @dra27]
diff --git a/src/repository/opamGit.ml b/src/repository/opamGit.ml
index c30f66a3162..49980641c77 100644
--- a/src/repository/opamGit.ml
+++ b/src/repository/opamGit.ml
@@ -62,7 +62,7 @@ module VCS : OpamVCS.VCS = struct
     | Some h -> "refs/remotes/opam-ref-"^h
     | None -> "refs/remotes/opam-ref"
 
-  let fetch ?(full_fetch = false) ?cache_dir ?subpath repo_root repo_url =
+  let fetch ?(full_fetch = true) ?cache_dir ?subpath repo_root repo_url =
     (match subpath with
      | Some sp ->
        git repo_root [ "config"; "--local"; "core.sparseCheckout"; "true" ]
diff --git a/src/repository/opamRepository.mli b/src/repository/opamRepository.mli
index f66a3a73c2e..babd92c3127 100644
--- a/src/repository/opamRepository.mli
+++ b/src/repository/opamRepository.mli
@@ -43,8 +43,8 @@ val pull_shared_tree:
   url list -> string download OpamProcess.job
 
 (* Same as [pull_shared_tree], but for a unique label/dirname.
-   If [full_fetch] is true, VCS repository is retrieved with full history (by
-   default, no history). *)
+   If [full_fetch] is set to false, VCS repository is retrieved with shallow
+   history (by default, full history). *)
 val pull_tree:
   string -> ?full_fetch:bool -> ?cache_dir:dirname -> ?cache_urls:url list ->
   ?working_dir:bool -> ?subpath:subpath ->
diff --git a/src/repository/opamRepositoryBackend.mli b/src/repository/opamRepositoryBackend.mli
index dcdb62fae1d..7d51025a6f7 100644
--- a/src/repository/opamRepositoryBackend.mli
+++ b/src/repository/opamRepositoryBackend.mli
@@ -45,8 +45,8 @@ module type S = sig
       [checksum] can be used for retrieval but is NOT checked by this
       function.
 
-      If [full_fetch] is set to true, VCS repository is retrieved with full
-      history (by default, no history).
+      If [full_fetch] is set to false, VCS repository is retrieved with shallow
+      history (by default, full history).
       If [cache_dir] is given, the directory is used by VCS tool as a its cache
       directory.
       If [subpath] is given, only that [subpath] of the url is retrieved. *)
diff --git a/src/repository/opamVCS.mli b/src/repository/opamVCS.mli
index 3a1d709ae29..d8fd5633dc8 100644
--- a/src/repository/opamVCS.mli
+++ b/src/repository/opamVCS.mli
@@ -29,8 +29,8 @@ module type VCS = sig
       Be aware that the remote URL might have been changed, so make sure
       to update accordingly.
 
-      If [full_fetch] is set to true, VCS repository is retrieved with full
-      history (by default, no history).
+      If [full_fetch] is set to false, VCS repository is retrieved with shallow
+      history (by default, full history).
       If [cache_dir] is given, the directory is used by VCS tool as a its cache
       directory.
       If [subpath] is given, only that [subpath] of the url is retrieved. *)
diff --git a/tests/reftests/fetch-package.test b/tests/reftests/fetch-package.test
index 9966ba3f92a..652229a8561 100644
--- a/tests/reftests/fetch-package.test
+++ b/tests/reftests/fetch-package.test
@@ -87,7 +87,7 @@ Done.
 opam
 root.ml
 ### cat OPAM/downloads-repo/lib/foo-git-hist
-1
+2
 ### :: pinning
 ### opam switch create downloads-pin --empty
 ### opam pin foo-arch-pin arch.tgz -y
@@ -124,7 +124,7 @@ Done.
 opam
 root.ml
 ### cat OPAM/downloads-pin/lib/foo-git-pin-hist
-1
+2
 ### :: dev-repo
 ### opam switch create downloads-devrepo --empty
 ### opam pin foo-git --dev-repo -y
@@ -143,4 +143,4 @@ Done.
 opam
 root.ml
 ### cat OPAM/downloads-devrepo/lib/foo-git-hist
-1
+2
diff --git a/tests/reftests/source.test b/tests/reftests/source.test
index e75374635f3..e1c5e3999bb 100644
--- a/tests/reftests/source.test
+++ b/tests/reftests/source.test
@@ -132,7 +132,7 @@ Now run 'opam upgrade' to apply any package updates.
 ### opam source pandore.4 --dir pandore5
 Successfully extracted to ${BASEDIR}/pandore5
 ### git -C pandore5 rev-list --all --count
-1
+2
 ### opam source pandore.4 --dev --dir pandore6
 Successfully fetched pandore development repo to ${BASEDIR}/pandore6
 ### git -C pandore6 rev-list --all --count