diff --git a/test/credits/canonical_names_test.rb b/test/credits/canonical_names_test.rb
index e15fd8a4..a43b160b 100644
--- a/test/credits/canonical_names_test.rb
+++ b/test/credits/canonical_names_test.rb
@@ -1460,7 +1460,7 @@ class CanonicalNamesTest < ActiveSupport::TestCase
     end
 
     test "evgeny.zislis\100gmail.com" do
-      assert_contributor_names '842ce34', 'Evgeny Zislis'
+      assert_contributor_names '842ce34b', 'Evgeny Zislis'
     end
 
     test 'f.svehla' do
@@ -2064,7 +2064,7 @@ class CanonicalNamesTest < ActiveSupport::TestCase
     end
 
     test "jeff\100ministrycentered.com" do
-      assert_contributor_names 'a5991d8', 'Jeff Berg'
+      assert_contributor_names 'a5991d84', 'Jeff Berg'
     end
 
     test "jeff\100opendbms.com" do
diff --git a/test/support/assert_contributor_names.rb b/test/support/assert_contributor_names.rb
index 6d77f54e..6c48aaa6 100644
--- a/test/support/assert_contributor_names.rb
+++ b/test/support/assert_contributor_names.rb
@@ -6,7 +6,11 @@ module AssertContributorNames
   def assert_contributor_names(sha1, *contributor_names, **options)
     begin
       commit = Commit.new_from_rugged_commit(REPO.repo.lookup(sha1))
-    rescue Rugged::OdbError
+    rescue Rugged::OdbError => e
+      if e.message == "ambiguous OID prefix - found multiple pack entries"
+        raise "#{sha1} is ambiguous, please use the full commit SHA"
+      end
+
       raise "#{sha1} was not found, please make sure the local Rails checkout is up to date"
     end