diff --git a/lib/DB.rakumod b/lib/DB.rakumod
index 7dfadf4..bbd3923 100644
--- a/lib/DB.rakumod
+++ b/lib/DB.rakumod
@@ -7,10 +7,13 @@ class SourceSpec {
 
     has Str $.rakudo-git-url = config.projects.rakudo.repo-url;
     has SHA1 $.rakudo-commit-sha = 'LATEST';
+    has Str $.rakudo-fetch-ref;
     has Str $.nqp-git-url = config.projects.nqp.repo-url;
     has SHA1 $.nqp-commit-sha = 'LATEST';
+    has Str $.nqp-fetch-ref;
     has Str $.moar-git-url = config.projects.moar.repo-url;
     has SHA1 $.moar-commit-sha = 'LATEST';
+    has Str $.moar-fetch-ref;
     
     submethod TWEAK() {
         $!rakudo-commit-sha .= uc;
@@ -157,10 +160,13 @@ model CITestSet is rw is table<citest_set> {
 
         has Str                   $!rakudo-git-url           is column{ :nullable };
         has Str                   $!rakudo-commit-sha        is column{ :nullable };
+        has Str                   $!rakudo-fetch-ref         is column{ :nullable };
         has Str                   $!nqp-git-url              is column{ :nullable };
         has Str                   $!nqp-commit-sha           is column{ :nullable };
+        has Str                   $!nqp-fetch-ref            is column{ :nullable };
         has Str                   $!moar-git-url             is column{ :nullable };
         has Str                   $!moar-commit-sha          is column{ :nullable };
+        has Str                   $!moar-fetch-ref           is column{ :nullable };
 
         has Str                   $.source-archive-id        is column{ :nullable, :type<text> };
         has UInt                  $.source-retrieval-retries is column = 0;
@@ -173,19 +179,25 @@ model CITestSet is rw is table<citest_set> {
     multi method source-spec($spec) {
         $!rakudo-git-url = $spec.rakudo-git-url;
         $!rakudo-commit-sha = $spec.rakudo-commit-sha;
+        $!rakudo-fetch-ref = $spec.rakudo-fetch-ref;
         $!nqp-git-url = $spec.nqp-git-url;
         $!nqp-commit-sha = $spec.nqp-commit-sha;
+        $!nqp-fetch-ref = $spec.nqp-fetch-ref;
         $!moar-git-url = $spec.moar-git-url;
         $!moar-commit-sha = $spec.moar-commit-sha;
+        $!moar-fetch-ref = $spec.moar-fetch-ref;
     }
     multi method source-spec() {
         SourceSpec.new(
             rakudo-git-url    => $!rakudo-git-url // "",
             rakudo-commit-sha => $!rakudo-commit-sha // "",
+            rakudo-fetch-ref  => $!rakudo-fetch-ref // "",
             nqp-git-url       => $!nqp-git-url // "",
             nqp-commit-sha    => $!nqp-commit-sha // "",
+            nqp-fetch-ref     => $!nqp-fetch-ref // "",
             moar-git-url      => $!moar-git-url // "",
             moar-commit-sha   => $!moar-commit-sha // "",
+            moar-fetch-ref    => $!moar-fetch-ref // "",
         )
     }
 }
diff --git a/lib/GitHubCITestRequester.rakumod b/lib/GitHubCITestRequester.rakumod
index 303df06..aa29579 100644
--- a/lib/GitHubCITestRequester.rakumod
+++ b/lib/GitHubCITestRequester.rakumod
@@ -276,6 +276,8 @@ method process-worklist() is serial-dedup {
         # NOT the head (the repo where the new commits are).
         # Using the head repo will not work, as that's usually a different repo where the RCB is
         # not installed on and thus has no permissons to add check_runs.
+        # In addition it's possible there is no head repo. That is the case when the branch or repo a
+        # PR is based on has been deleted.
         # One would think using the base repo can't work, because the commits are not part of that
         # repository. But there is some almost completely undocumented behavior in GitHub that copies
         # PR commits to the base repo and even creates merge commits (without the PR being merged!).
@@ -330,7 +332,8 @@ method process-worklist() is serial-dedup {
 
 method !determine-source-spec(:$project!, :$git-url!, :$commit-sha!, :$pr --> SourceSpec) {
     my ($rakudo-git-url, $nqp-git-url, $moar-git-url,
-        $rakudo-commit-sha, $nqp-commit-sha, $moar-commit-sha);
+        $rakudo-commit-sha, $nqp-commit-sha, $moar-commit-sha,
+        $rakudo-fetch-ref, $nqp-fetch-ref, $moar-fetch-ref);
     my $did-things = False;
     with $pr {
         my %head-data = self!github-url-to-project-repo($pr.head-url);
@@ -354,13 +357,14 @@ method !determine-source-spec(:$project!, :$git-url!, :$commit-sha!, :$pr --> So
 
             my $branch = $pr.head-branch;
 
-            for DB::RAKUDO, $rakudo-git-url, $rakudo-commit-sha, $r-proj, $r-repo,
-                    DB::NQP, $nqp-git-url, $nqp-commit-sha, $n-proj, $n-repo,
-                    DB::MOAR, $moar-git-url, $moar-commit-sha, $m-proj, $m-repo
-            -> $cur-proj, $out-url is rw, $out-commit-sha is rw, $gh-project, $repo {
+            for DB::RAKUDO, $rakudo-git-url, $rakudo-commit-sha, $rakudo-fetch-ref, $r-proj, $r-repo,
+                    DB::NQP, $nqp-git-url, $nqp-commit-sha, $nqp-fetch-ref, $n-proj, $n-repo,
+                    DB::MOAR, $moar-git-url, $moar-commit-sha, $moar-fetch-ref, $m-proj, $m-repo
+            -> $cur-proj, $out-url is rw, $out-commit-sha is rw, $out-fetch-ref is rw, $gh-project, $repo {
                 if $cur-proj == $project {
-                    $out-url = $git-url;
+                    $out-url = $pr.base-url;
                     $out-commit-sha = $commit-sha;
+                    $out-fetch-ref = "pull/{$pr.number}/head";
                 }
                 else {
                     my $branch-data = $!github-interface.get-branch(:owner($gh-project), :$repo, :$branch);
@@ -381,18 +385,39 @@ method !determine-source-spec(:$project!, :$git-url!, :$commit-sha!, :$pr --> So
         }
     }
     if !$did-things {
-        given $project {
-            when DB::RAKUDO {
-                $rakudo-git-url = $git-url;
-                $rakudo-commit-sha = $commit-sha;
-            }
-            when DB::NQP {
-                $nqp-git-url = $git-url;
-                $nqp-commit-sha = $commit-sha;
+        with $pr {
+            given $project {
+                when DB::RAKUDO {
+                    $rakudo-git-url = $pr.base-url;
+                    $rakudo-commit-sha = $commit-sha;
+                    $rakudo-fetch-ref = "pull/{$pr.number}/head";
+                }
+                when DB::NQP {
+                    $nqp-git-url = $pr.base-url;
+                    $nqp-commit-sha = $commit-sha;
+                    $nqp-fetch-ref = "pull/{$pr.number}/head";
+                }
+                when DB::MOAR {
+                    $moar-git-url = $pr.base-url;
+                    $moar-commit-sha = $commit-sha;
+                    $moar-fetch-ref = "pull/{$pr.number}/head";
+                }
             }
-            when DB::MOAR {
-                $moar-git-url = $git-url;
-                $moar-commit-sha = $commit-sha;
+        }
+        else {
+            given $project {
+                when DB::RAKUDO {
+                    $rakudo-git-url = $git-url;
+                    $rakudo-commit-sha = $commit-sha;
+                }
+                when DB::NQP {
+                    $nqp-git-url = $git-url;
+                    $nqp-commit-sha = $commit-sha;
+                }
+                when DB::MOAR {
+                    $moar-git-url = $git-url;
+                    $moar-commit-sha = $commit-sha;
+                }
             }
         }
     }
@@ -400,10 +425,13 @@ method !determine-source-spec(:$project!, :$git-url!, :$commit-sha!, :$pr --> So
     return SourceSpec.new:
         |($rakudo-git-url    ?? :$rakudo-git-url    !! ()),
         |($rakudo-commit-sha ?? :$rakudo-commit-sha !! ()),
+        |($rakudo-fetch-ref  ?? :$rakudo-fetch-ref  !! ()),
         |($nqp-git-url       ?? :$nqp-git-url       !! ()),
         |($nqp-commit-sha    ?? :$nqp-commit-sha    !! ()),
+        |($nqp-fetch-ref     ?? :$nqp-fetch-ref     !! ()),
         |($moar-git-url      ?? :$moar-git-url      !! ()),
         |($moar-commit-sha   ?? :$moar-commit-sha   !! ()),
+        |($moar-fetch-ref    ?? :$moar-fetch-ref    !! ()),
 }
 
 method !github-url-to-project-repo($url) {
diff --git a/lib/SourceArchiveCreator.rakumod b/lib/SourceArchiveCreator.rakumod
index 97695f6..b50a731 100644
--- a/lib/SourceArchiveCreator.rakumod
+++ b/lib/SourceArchiveCreator.rakumod
@@ -108,10 +108,10 @@ method create-archive(DB::CITestSet $test-set) {
         }
 
         my @shas;
-        for $!rakudo-dir, $source-spec.rakudo-git-url, $source-spec.rakudo-commit-sha, config.projects.rakudo.main,
-                $!nqp-dir,    $source-spec.nqp-git-url, $source-spec.nqp-commit-sha, config.projects.nqp.main,
-                $!moar-dir,   $source-spec.moar-git-url, $source-spec.moar-commit-sha, config.projects.moar.main
-                -> $repo-dir, $remote, $commit, $main {
+        for $!rakudo-dir,   $source-spec.rakudo-git-url, $source-spec.rakudo-commit-sha, $source-spec.rakudo-fetch-ref, config.projects.rakudo.main,
+                $!nqp-dir,  $source-spec.nqp-git-url,    $source-spec.nqp-commit-sha,    $source-spec.nqp-fetch-ref,    config.projects.nqp.main,
+                $!moar-dir, $source-spec.moar-git-url,   $source-spec.moar-commit-sha,   $source-spec.moar-fetch-ref,   config.projects.moar.main
+                -> $repo-dir, $remote, $commit, $fetch-ref, $main {
             debug "SourceArchiveCreator: working on " ~ $remote ~ " " ~ $commit;
             my $tmp-branch = 'tmp-branch';
 
@@ -121,8 +121,7 @@ method create-archive(DB::CITestSet $test-set) {
             validate run qw|git remote add|, $tmp-branch, $remote,
                 :cwd($repo-dir), :merge;
 
-            #validate run qw|git fetch|, $tmp-branch, |($.fetch-ref ?? ("+refs/" ~ $.fetch-ref ~ ":refs/remotes/" ~ $.fetch-ref,) !! ()),
-            validate run qw|git fetch|, $tmp-branch,
+            validate run qw|git fetch|, $tmp-branch, |($fetch-ref ?? ("+refs/" ~ $fetch-ref ~ ":refs/remotes/" ~ $fetch-ref,) !! ()),
                 :cwd($repo-dir), :merge;
 
             my $ref = $commit eq 'LATEST' ?? "$tmp-branch/$main" !! $commit;