diff --git a/src/Famix-Value-Importer/Dictionary.extension.st b/src/Famix-Value-Importer/Dictionary.extension.st
index 4cc7dcd..8fa2fcd 100644
--- a/src/Famix-Value-Importer/Dictionary.extension.st
+++ b/src/Famix-Value-Importer/Dictionary.extension.st
@@ -3,7 +3,7 @@ Extension { #name : #Dictionary }
 { #category : #'*Famix-Value-Importer' }
 Dictionary >> asPharoJacksonValueOn: importer [
 
-	^ (self removeKey: importer typeKey ifAbsent: nil)
+	^ (importer getObjectType: self)
 		  ifNotNil: [ :className | "object of an unloaded class"
 			  className = 'Class'
 				  ifTrue: [
@@ -15,7 +15,7 @@ Dictionary >> asPharoJacksonValueOn: importer [
 					  importObject: self
 					  of: (importer loadTypeNamed: className) ] ]
 		  ifNil: [ "species of dictionary"
-			  (self removeKey: importer refKey ifAbsent: nil)
+			  (importer getObjectReference: self)
 				  ifNotNil: [ :refId | "if @ref"
 					  importer
 						  getObjectFromIdentity: refId
diff --git a/src/Famix-Value-Importer/FamixValueJavaJacksonImporter.class.st b/src/Famix-Value-Importer/FamixValueJavaJacksonImporter.class.st
index fe94f57..8badc65 100644
--- a/src/Famix-Value-Importer/FamixValueJavaJacksonImporter.class.st
+++ b/src/Famix-Value-Importer/FamixValueJavaJacksonImporter.class.st
@@ -36,6 +36,12 @@ FamixValueJavaJacksonImporter >> getObjectIdentity: rawObject [
 	^ rawObject removeKey: self idKey ifAbsent: nil
 ]
 
+{ #category : #enumerating }
+FamixValueJavaJacksonImporter >> getObjectType: rawObject [
+
+	^ rawObject removeKey: self typeKey ifAbsent: nil
+]
+
 { #category : #accessing }
 FamixValueJavaJacksonImporter >> idKey [
 
@@ -62,6 +68,10 @@ FamixValueJavaJacksonImporter >> importClassReference: rawValue of: type [
 FamixValueJavaJacksonImporter >> importObjectAttribute: rawValue of: type named: name [
 
 	| attribute |
+	type isInterface ifTrue: [
+		Error signal:
+			'Cannot find attributes in interfaces. Signaled for attribute `'
+			, name , '` and interface `' , type name , '`.' ].
 	(attribute := type findAttributeNamed: name) ifNotNil: [ "Skip transient attributes."
 		attribute isTransient ifTrue: [ ^ nil ] ].
 	^ self
diff --git a/src/Famix-Value-Importer/FamixValuePharoJacksonImporter.class.st b/src/Famix-Value-Importer/FamixValuePharoJacksonImporter.class.st
index df709a9..d4ae209 100644
--- a/src/Famix-Value-Importer/FamixValuePharoJacksonImporter.class.st
+++ b/src/Famix-Value-Importer/FamixValuePharoJacksonImporter.class.st
@@ -24,6 +24,18 @@ FamixValuePharoJacksonImporter >> getObjectIdentity: rawObject [
 	^ rawObject removeKey: self idKey ifAbsent: nil
 ]
 
+{ #category : #enumerating }
+FamixValuePharoJacksonImporter >> getObjectReference: rawObject [
+
+	^ rawObject removeKey: self refKey ifAbsent: nil
+]
+
+{ #category : #enumerating }
+FamixValuePharoJacksonImporter >> getObjectType: rawObject [
+
+	^ rawObject removeKey: self typeKey ifAbsent: nil
+]
+
 { #category : #accessing }
 FamixValuePharoJacksonImporter >> idKey [
 
diff --git a/src/Famix-Value-Importer/OrderedDictionary.extension.st b/src/Famix-Value-Importer/OrderedDictionary.extension.st
index 13296d1..3093c87 100644
--- a/src/Famix-Value-Importer/OrderedDictionary.extension.st
+++ b/src/Famix-Value-Importer/OrderedDictionary.extension.st
@@ -4,11 +4,11 @@ Extension { #name : #OrderedDictionary }
 OrderedDictionary >> asJavaJacksonValueOn: importer [
 
 	| type |
-	(self removeKey: importer typeKey ifAbsent: nil)
-		ifNotNil: [ :typeName | type := importer loadTypeNamed: typeName ]
-		ifNil: [
-			(type := importer typeInference) ifNil: [
-				self error: 'Cannot determine type.' ] ].
+	type := (importer getObjectType: self)
+		        ifNotNil: [ :typeName | importer loadTypeNamed: typeName ]
+		        ifNil: [
+			        importer typeInference ifNil: [
+				        Error signal: 'Cannot determine type.' ] ].
 	^ (type isUnknownType or: [ type isDictionaryType ])
 		  ifTrue: [ importer importDictionary: self of: type ]
 		  ifFalse: [ importer importObject: self of: type ]
@@ -17,7 +17,7 @@ OrderedDictionary >> asJavaJacksonValueOn: importer [
 { #category : #'*Famix-Value-Importer' }
 OrderedDictionary >> asPharoJacksonValueOn: importer [
 
-	^ (self removeKey: importer typeKey ifAbsent: nil)
+	^ (importer getObjectType: self)
 		  ifNotNil: [ :className | "object of an unloaded class"
 			  className = 'Class'
 				  ifTrue: [
@@ -29,7 +29,7 @@ OrderedDictionary >> asPharoJacksonValueOn: importer [
 					  importObject: self
 					  of: (importer loadTypeNamed: className) ] ]
 		  ifNil: [ "species of dictionary"
-			  (self removeKey: importer refKey ifAbsent: nil)
+			  (importer getObjectReference: self)
 				  ifNotNil: [ :refId | "if @ref"
 					  importer
 						  getObjectFromIdentity: refId