diff --git a/src/lib/Hydra/Helper/AddBuilds.pm b/src/lib/Hydra/Helper/AddBuilds.pm
index f1e21b49..ec62811d 100644
--- a/src/lib/Hydra/Helper/AddBuilds.pm
+++ b/src/lib/Hydra/Helper/AddBuilds.pm
@@ -433,7 +433,7 @@ sub checkBuild {
                 { rows => 1, columns => ['id'], join => ['buildoutputs'] });
             if (defined $prevBuild) {
                 print STDERR "    already scheduled/built as build ", $prevBuild->id, "\n";
-                $buildMap->{$prevBuild->id} = { new => 0, drvPath => $drvPath };
+                $buildMap->{$prevBuild->id} = { id => $prevBuild->id, jobName => $jobName, new => 0, drvPath => $drvPath };
                 return;
             }
         }
@@ -506,7 +506,7 @@ sub checkBuild {
         $build->buildoutputs->create({ name => $_, path => $buildInfo->{output}->{$_}->{path} })
             foreach @outputNames;
 
-        $buildMap->{$build->id} = { new => 1, drvPath => $drvPath };
+        $buildMap->{$build->id} = { id => $build->id, jobName => $jobName, new => 1, drvPath => $drvPath };
         $$jobOutPathMap{$jobName . "\t" . $firstOutputPath} = $build->id;
 
         if ($build->iscachedbuild) {
diff --git a/src/script/hydra-evaluator b/src/script/hydra-evaluator
index 0fdca76a..7505b93b 100755
--- a/src/script/hydra-evaluator
+++ b/src/script/hydra-evaluator
@@ -177,20 +177,31 @@ sub checkJobsetWrapped {
 
         if ($hasNewBuilds) {
             # Create JobsetEvalMembers mappings.
-            my %drvPathToId;
             while (my ($id, $x) = each %buildMap) {
                 $ev->jobsetevalmembers->create({ build => $id, isnew => $x->{new} });
-                $drvPathToId{$x->{drvPath}} = $id;
             }
 
-            # Create AggregateConstituents mappings.
+            # Create AggregateConstituents mappings.  Since there can
+            # be jobs that alias each other, if there are multiple
+            # builds for the same derivation, pick the one with the
+            # shortest name.
+            my %drvPathToId;
+            while (my ($id, $x) = each %buildMap) {
+                my $y = $drvPathToId{$x->{drvPath}};
+                if (defined $y) {
+                    next if length $x->{jobName} > length $y->{jobName};
+                    next if length $x->{jobName} == length $y->{jobName} && $x->{jobName} ge $y->{jobName};
+                }
+                $drvPathToId{$x->{drvPath}} = $x;
+            }
+
             foreach my $job (@{$jobs->{job}}) {
                 next unless $job->{constituents};
-                my $id = $drvPathToId{$job->{drvPath}} or die;
+                my $x = $drvPathToId{$job->{drvPath}} or die;
                 foreach my $drvPath (split / /, $job->{constituents}) {
                     my $constituent = $drvPathToId{$drvPath};
                     if (defined $constituent) {
-                        $db->resultset('AggregateConstituents')->update_or_create({aggregate => $id, constituent => $constituent});
+                        $db->resultset('AggregateConstituents')->update_or_create({aggregate => $x->{id}, constituent => $constituent->{id}});
                     } else {
                         warn "aggregate job ‘$job->{jobName}’ has a constituent ‘$drvPath’ that doesn't correspond to a Hydra build\n";
                     }