diff --git a/master_changes.md b/master_changes.md
index aef29e1f5d8..f8e7ba1eccb 100644
--- a/master_changes.md
+++ b/master_changes.md
@@ -56,6 +56,8 @@ users)
 ## Var/Option
 
 ## Update / Upgrade
+  * [BUG] Fix a regression on `opam upgrade <package>` upgrading unrelated packages [#6373 @AltGr]
+  * [BUG] Fix a regression on `opam upgrade --all <uninstalled-pkg>` not upgrading the whole switch [#6373 @kit-ty-kate]
 
 ## Tree
 
@@ -162,6 +164,7 @@ users)
   * Extend the tests on opam admin to include packages using builtin global variables [#6331 @kit-ty-kate]
   * Extend the tests on opam admin check by including all the arguments [#6331 @kit-ty-kate @rjbou]
   * Add double pinning test in case of opam/opam opam file [#6343 @rjbou]
+  * Add a test to ensure `opam upgrade <pkg>` will not upgrade unrelated things [#6373 @kit-ty-kate]
 
 ### Engine
 
diff --git a/src/client/opamClient.ml b/src/client/opamClient.ml
index 2b37a6f6fcc..801e250faa0 100644
--- a/src/client/opamClient.ml
+++ b/src/client/opamClient.ml
@@ -113,27 +113,16 @@ let compute_upgrade_t
         | Some nv -> not (OpamPackage.Set.mem nv (Lazy.force t.available_packages)))
       atoms
   in
-  let criteria = if to_install = [] then `Upgrade else `Default in
-  if all then
-    names,
-    OpamSolution.resolve t Upgrade
-      ~requested:packages
-      ~reinstall:(Lazy.force t.reinstall)
-      (OpamSolver.request
-         ~install:to_install
-         ~upgrade:to_upgrade
-         ~deprequest:(OpamFormula.to_atom_formula formula)
-         ~all:[]
-         ~criteria ())
-  else
   names,
   OpamSolution.resolve t Upgrade
     ~requested:packages
+    ?reinstall:(if all then Some (Lazy.force t.reinstall) else None)
     (OpamSolver.request
        ~install:to_install
        ~upgrade:to_upgrade
        ~deprequest:(OpamFormula.to_atom_formula formula)
-       ~criteria
+       ?all:(if all then Some [] else None)
+       ~criteria:(if all then `Upgrade else `Default)
        ())
 
 let print_requested requested formula =
diff --git a/tests/reftests/upgrade.test b/tests/reftests/upgrade.test
index 29d809de5ae..343ab53c479 100644
--- a/tests/reftests/upgrade.test
+++ b/tests/reftests/upgrade.test
@@ -384,3 +384,83 @@ Done.
 # Packages matching: name-match(quux) & installed
 # Name # Installed files
 quux   ${BASEDIR}/OPAM/upgrading/lib/quux ${BASEDIR}/OPAM/upgrading/lib/quux/fichier
+### :::::::::::::::::::::::
+### : Make sure opam upgrade <pkg> only tries to upgrade <pkg> and not anything else
+### :::::::::::::::::::::::
+### opam upgrade
+Already up-to-date.
+Nothing to do.
+### <pkg:foo.4>
+opam-version: "2.0"
+### <pkg:bar.3>
+opam-version: "2.0"
+### <pkg:baz.2>
+opam-version: "2.0"
+depends: "foo"
+### <pkg:uninstalled.1>
+opam-version: "2.0"
+### opam upgrade --show foo
+The following actions would be performed:
+=== upgrade 1 package
+  - upgrade foo 3 to 4
+### opam upgrade --show -a foo
+The following actions would be performed:
+=== upgrade 3 packages
+  - upgrade bar 2 to 3
+  - upgrade baz 1 to 2 [uses foo]
+  - upgrade foo 3 to 4
+### opam upgrade --show bar
+The following actions would be performed:
+=== upgrade 1 package
+  - upgrade bar 2 to 3
+### opam upgrade --show -a bar
+The following actions would be performed:
+=== upgrade 3 packages
+  - upgrade bar 2 to 3
+  - upgrade baz 1 to 2 [uses foo]
+  - upgrade foo 3 to 4
+### opam upgrade --show baz
+The following actions would be performed:
+=== upgrade 1 package
+  - upgrade baz 1 to 2
+### opam upgrade --show -a baz
+The following actions would be performed:
+=== upgrade 3 packages
+  - upgrade bar 2 to 3
+  - upgrade baz 1 to 2
+  - upgrade foo 3 to 4 [required by baz]
+### opam upgrade --show uninstalled
+uninstalled is not installed. Install it? [Y/n] y
+The following actions would be performed:
+=== install 1 package
+  - install uninstalled 1
+### opam upgrade --show -a uninstalled
+uninstalled is not installed. Install it? [Y/n] y
+The following actions would be performed:
+=== upgrade 3 packages
+  - upgrade bar         2 to 3
+  - upgrade baz         1 to 2 [uses foo]
+  - upgrade foo         3 to 4
+=== install 1 package
+  - install uninstalled 1
+### opam upgrade --show
+The following actions would be performed:
+=== upgrade 3 packages
+  - upgrade bar 2 to 3
+  - upgrade baz 1 to 2
+  - upgrade foo 3 to 4
+### opam upgrade baz
+The following actions will be performed:
+=== upgrade 1 package
+  - upgrade baz 1 to 2
+
+<><> Processing actions <><><><><><><><><><><><><><><><><><><><><><><><><><><><>
+-> removed   baz.1
+-> installed baz.2
+Done.
+### opam upgrade --show foo
+The following actions would be performed:
+=== recompile 1 package
+  - recompile baz 2      [uses foo]
+=== upgrade 1 package
+  - upgrade   foo 3 to 4