diff --git a/source/Sagan-Core-Tests/RepositoryBasedTest.class.st b/source/Sagan-Core-Tests/RepositoryBasedTest.class.st
index 2f94d18..a2889f6 100644
--- a/source/Sagan-Core-Tests/RepositoryBasedTest.class.st
+++ b/source/Sagan-Core-Tests/RepositoryBasedTest.class.st
@@ -321,9 +321,10 @@ RepositoryBasedTest >> testStoreIdentical [
 	self extraterrestrials store: instance.
 
 	found := self extraterrestrials findAll.
-	self assert: found size equals: 2.
-	self assert: ( found allSatisfy: [ :extraterrestrial |
-			  extraterrestrial firstName = 'Silvester' and: [ extraterrestrial lastName = 'Stallone' ] ] )
+	self withTheOnlyOneIn: found do: [ :extraterrestrial |
+		self assert:
+			( extraterrestrial firstName = 'Silvester' and: [ extraterrestrial lastName = 'Stallone' ] )
+		]
 ]
 
 { #category : 'tests - conflict checking' }
diff --git a/source/Sagan-Core/InMemoryRepository.class.st b/source/Sagan-Core/InMemoryRepository.class.st
index 3258076..99eb9d4 100644
--- a/source/Sagan-Core/InMemoryRepository.class.st
+++ b/source/Sagan-Core/InMemoryRepository.class.st
@@ -66,7 +66,7 @@ InMemoryRepository >> findAllMatching: aCriteriaOrBlock sortedBy: aSortFunction
 InMemoryRepository >> initializeCheckingConflictsAccordingTo: aConflictCheckingStrategy [
 
 	conflictCheckingStrategy := aConflictCheckingStrategy.
-	contents := OrderedCollection new
+	contents := Set new
 ]
 
 { #category : 'private - accessing' }