diff --git a/src/shogun/converter/Converter.h b/src/shogun/converter/Converter.h
index faf280b2cf0..9a042d9dd95 100644
--- a/src/shogun/converter/Converter.h
+++ b/src/shogun/converter/Converter.h
@@ -9,9 +9,10 @@
 
 #include <shogun/lib/config.h>
 
-#include <shogun/lib/common.h>
 #include <shogun/base/SGObject.h>
 #include <shogun/features/Features.h>
+#include <shogun/lib/common.h>
+#include <shogun/transformer/Transformer.h>
 
 namespace shogun
 {
@@ -19,11 +20,11 @@ namespace shogun
 /** @brief class Converter used to convert data
  *
  */
-class CConverter : public CSGObject
+class CConverter : public CTransformer
 {
 public:
 	/** constructor */
-	CConverter() : CSGObject() {};
+	CConverter() : CTransformer(){};
 
 	/** destructor */
 	virtual ~CConverter() {};
diff --git a/src/shogun/preprocessor/Preprocessor.h b/src/shogun/preprocessor/Preprocessor.h
index d3e8d6ab0d6..937ae865b3e 100644
--- a/src/shogun/preprocessor/Preprocessor.h
+++ b/src/shogun/preprocessor/Preprocessor.h
@@ -10,10 +10,11 @@
 
 #include <shogun/lib/config.h>
 
-#include <shogun/lib/common.h>
 #include <shogun/base/SGObject.h>
 #include <shogun/features/FeatureTypes.h>
 #include <shogun/features/Features.h>
+#include <shogun/lib/common.h>
+#include <shogun/transformer/Transformer.h>
 
 namespace shogun
 {
@@ -67,22 +68,17 @@ enum EPreprocessorType
  * an abstract apply() method is there, which sub-classes may choose to use as
  * a wrapper to more specific methods.
  */
-class CPreprocessor : public CSGObject
+class CPreprocessor : public CTransformer
 {
 public:
 	/** constructor */
-	CPreprocessor() : CSGObject()
-	{
-	};
+	CPreprocessor() : CTransformer(){};
 
 	/** destructor */
 	virtual ~CPreprocessor()
 	{
 	}
 
-	/** initialize preprocessor with features */
-	virtual bool init(CFeatures* features)=0;
-
 	/** generic interface for applying the preprocessor. sub-classes may use
 	 * this method as a wrapper to specific implementations
 	 *