diff --git a/src/Moose-SmalltalkImporter/FamixStModel.extension.st b/src/Moose-SmalltalkImporter/FamixStModel.extension.st
new file mode 100644
index 000000000..6d20347db
--- /dev/null
+++ b/src/Moose-SmalltalkImporter/FamixStModel.extension.st
@@ -0,0 +1,25 @@
+Extension { #name : #FamixStModel }
+
+{ #category : #'*Moose-SmalltalkImporter' }
+FamixStModel >> newModelAddingAll: classesAndPackages [
+	"Returns a new model with all current entities plus the requested classes and packages."
+
+	| model task request |
+	task := FamixStPharoImporterTask new
+		        model: (model := self class named: name);
+		        importingContext:
+			        FamixStImporterContext new mergeClassAndMetaclass
+				        importMaximum.
+
+	request := (self entityStorage selectAllWithType: FamixStPackage)
+		           collect: [ :famixPackage | famixPackage name asPackage ]
+		           as: Set.
+	request addAll: classesAndPackages.
+	request do: [ :classOrPackage |
+		classOrPackage isClass
+			ifTrue: [ task addClass: classOrPackage ]
+			ifFalse: [ task addFromPackage: classOrPackage ] ].
+
+	task runWithProgress.
+	^ model "no install: not added to root and groups not cached"
+]