diff --git a/code/Assimp.cpp b/code/Assimp.cpp
index 89b62d110..ef5b0d9bc 100644
--- a/code/Assimp.cpp
+++ b/code/Assimp.cpp
@@ -483,7 +483,7 @@ ASSIMP_API void aiSetImportPropertyInteger(aiPropertyStore* p, const char* szNam
 {
 	ASSIMP_BEGIN_EXCEPTION_REGION();
 	PropertyMap* pp = reinterpret_cast<PropertyMap*>(p);
-	SetGenericProperty<int>(pp->ints,szName,value,NULL);
+	SetGenericProperty<int>(pp->ints,szName,value);
 	ASSIMP_END_EXCEPTION_REGION(void);
 }
 
@@ -493,7 +493,7 @@ ASSIMP_API void aiSetImportPropertyFloat(aiPropertyStore* p, const char* szName,
 {
 	ASSIMP_BEGIN_EXCEPTION_REGION();
 	PropertyMap* pp = reinterpret_cast<PropertyMap*>(p);
-	SetGenericProperty<float>(pp->floats,szName,value,NULL);
+	SetGenericProperty<float>(pp->floats,szName,value);
 	ASSIMP_END_EXCEPTION_REGION(void);
 }
 
@@ -507,7 +507,7 @@ ASSIMP_API void aiSetImportPropertyString(aiPropertyStore* p, const char* szName
 	}
 	ASSIMP_BEGIN_EXCEPTION_REGION();
 	PropertyMap* pp = reinterpret_cast<PropertyMap*>(p);
-	SetGenericProperty<std::string>(pp->strings,szName,std::string(st->C_Str()),NULL);
+	SetGenericProperty<std::string>(pp->strings,szName,std::string(st->C_Str()));
 	ASSIMP_END_EXCEPTION_REGION(void);
 }
 
@@ -521,7 +521,7 @@ ASSIMP_API void aiSetImportPropertyMatrix(aiPropertyStore* p, const char* szName
 	}
 	ASSIMP_BEGIN_EXCEPTION_REGION();
 	PropertyMap* pp = reinterpret_cast<PropertyMap*>(p);
-	SetGenericProperty<aiMatrix4x4>(pp->matrices,szName,*mat,NULL);
+	SetGenericProperty<aiMatrix4x4>(pp->matrices,szName,*mat);
 	ASSIMP_END_EXCEPTION_REGION(void);
 }
 
diff --git a/code/Exporter.cpp b/code/Exporter.cpp
index c6fea8856..a0488e0f3 100644
--- a/code/Exporter.cpp
+++ b/code/Exporter.cpp
@@ -507,34 +507,30 @@ ExportProperties::ExportProperties(const ExportProperties &other)
 
 // ------------------------------------------------------------------------------------------------
 // Set a configuration property
-void ExportProperties :: SetPropertyInteger(const char* szName, int iValue, 
-	bool* bWasExisting /*= NULL*/)
+bool ExportProperties :: SetPropertyInteger(const char* szName, int iValue)
 {
-	SetGenericProperty<int>(mIntProperties, szName,iValue,bWasExisting);
+	return SetGenericProperty<int>(mIntProperties, szName,iValue);
 }
 
 // ------------------------------------------------------------------------------------------------
 // Set a configuration property
-void ExportProperties :: SetPropertyFloat(const char* szName, float iValue, 
-	bool* bWasExisting /*= NULL*/)
+bool ExportProperties :: SetPropertyFloat(const char* szName, float iValue)
 {
-	SetGenericProperty<float>(mFloatProperties, szName,iValue,bWasExisting);
+	return SetGenericProperty<float>(mFloatProperties, szName,iValue);
 }
 
 // ------------------------------------------------------------------------------------------------
 // Set a configuration property
-void ExportProperties :: SetPropertyString(const char* szName, const std::string& value, 
-	bool* bWasExisting /*= NULL*/)
+bool ExportProperties :: SetPropertyString(const char* szName, const std::string& value)
 {
-	SetGenericProperty<std::string>(mStringProperties, szName,value,bWasExisting);
+	return SetGenericProperty<std::string>(mStringProperties, szName,value);
 }
 
 // ------------------------------------------------------------------------------------------------
 // Set a configuration property
-void ExportProperties :: SetPropertyMatrix(const char* szName, const aiMatrix4x4& value, 
-	bool* bWasExisting /*= NULL*/)
+bool ExportProperties :: SetPropertyMatrix(const char* szName, const aiMatrix4x4& value)
 {
-	SetGenericProperty<aiMatrix4x4>(mMatrixProperties, szName,value,bWasExisting);
+	return SetGenericProperty<aiMatrix4x4>(mMatrixProperties, szName,value);
 }
 
 // ------------------------------------------------------------------------------------------------
diff --git a/code/GenericProperty.h b/code/GenericProperty.h
index 0e89015ab..06e6f7ca1 100644
--- a/code/GenericProperty.h
+++ b/code/GenericProperty.h
@@ -46,22 +46,19 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 // ------------------------------------------------------------------------------------------------
 template <class T>
-inline void SetGenericProperty(std::map< unsigned int, T >& list, 
-	const char* szName, const T& value, bool* bWasExisting = NULL)
+inline bool SetGenericProperty(std::map< unsigned int, T >& list, 
+	const char* szName, const T& value)
 {
 	ai_assert(NULL != szName);
 	const uint32_t hash = SuperFastHash(szName);
 
 	typename std::map<unsigned int, T>::iterator it = list.find(hash);
 	if (it == list.end())	{
-		if (bWasExisting)
-			*bWasExisting = false;
 		list.insert(std::pair<unsigned int, T>( hash, value ));
-		return;
+		return false;
 	}
 	(*it).second = value;
-	if (bWasExisting)
-		*bWasExisting = true;
+	return true;
 }
 
 // ------------------------------------------------------------------------------------------------
diff --git a/code/Importer.cpp b/code/Importer.cpp
index a9173cddc..1c45ff978 100644
--- a/code/Importer.cpp
+++ b/code/Importer.cpp
@@ -919,42 +919,46 @@ void Importer::GetExtensionList(aiString& szOut) const
 
 // ------------------------------------------------------------------------------------------------
 // Set a configuration property
-void Importer::SetPropertyInteger(const char* szName, int iValue, 
-	bool* bWasExisting /*= NULL*/)
+bool Importer::SetPropertyInteger(const char* szName, int iValue)
 {
+	bool exising;
 	ASSIMP_BEGIN_EXCEPTION_REGION();
-		SetGenericProperty<int>(pimpl->mIntProperties, szName,iValue,bWasExisting);	
-	ASSIMP_END_EXCEPTION_REGION(void);
+		exising = SetGenericProperty<int>(pimpl->mIntProperties, szName,iValue);	
+	ASSIMP_END_EXCEPTION_REGION(bool);
+	return exising;
 }
 
 // ------------------------------------------------------------------------------------------------
 // Set a configuration property
-void Importer::SetPropertyFloat(const char* szName, float iValue, 
-	bool* bWasExisting /*= NULL*/)
+bool Importer::SetPropertyFloat(const char* szName, float iValue)
 {
+	bool exising;
 	ASSIMP_BEGIN_EXCEPTION_REGION();
-		SetGenericProperty<float>(pimpl->mFloatProperties, szName,iValue,bWasExisting);	
-	ASSIMP_END_EXCEPTION_REGION(void);
+		exising = SetGenericProperty<float>(pimpl->mFloatProperties, szName,iValue);	
+	ASSIMP_END_EXCEPTION_REGION(bool);
+	return exising;
 }
 
 // ------------------------------------------------------------------------------------------------
 // Set a configuration property
-void Importer::SetPropertyString(const char* szName, const std::string& value, 
-	bool* bWasExisting /*= NULL*/)
+bool Importer::SetPropertyString(const char* szName, const std::string& value)
 {
+	bool exising;
 	ASSIMP_BEGIN_EXCEPTION_REGION();
-		SetGenericProperty<std::string>(pimpl->mStringProperties, szName,value,bWasExisting);	
-	ASSIMP_END_EXCEPTION_REGION(void);
+		exising = SetGenericProperty<std::string>(pimpl->mStringProperties, szName,value);	
+	ASSIMP_END_EXCEPTION_REGION(bool);
+	return exising;
 }
 
 // ------------------------------------------------------------------------------------------------
 // Set a configuration property
-void Importer::SetPropertyMatrix(const char* szName, const aiMatrix4x4& value, 
-	bool* bWasExisting /*= NULL*/)
+bool Importer::SetPropertyMatrix(const char* szName, const aiMatrix4x4& value)
 {
+	bool exising;
 	ASSIMP_BEGIN_EXCEPTION_REGION();
-	SetGenericProperty<aiMatrix4x4>(pimpl->mMatrixProperties, szName,value,bWasExisting);	
-	ASSIMP_END_EXCEPTION_REGION(void);
+		exising = SetGenericProperty<aiMatrix4x4>(pimpl->mMatrixProperties, szName,value);	
+	ASSIMP_END_EXCEPTION_REGION(bool);
+	return exising;
 }
 
 // ------------------------------------------------------------------------------------------------
diff --git a/code/MD3Loader.cpp b/code/MD3Loader.cpp
index 49cecd1bf..701f8db81 100644
--- a/code/MD3Loader.cpp
+++ b/code/MD3Loader.cpp
@@ -556,7 +556,7 @@ bool MD3Importer::ReadMultipartFile()
 
 		// ensure we won't try to load ourselves recursively
 		BatchLoader::PropertyMap props;
-		SetGenericProperty( props.ints, AI_CONFIG_IMPORT_MD3_HANDLE_MULTIPART, 0, NULL);
+		SetGenericProperty( props.ints, AI_CONFIG_IMPORT_MD3_HANDLE_MULTIPART, 0);
 
 		// now read these three files
 		BatchLoader batch(mIOHandler);
diff --git a/include/assimp/Exporter.hpp b/include/assimp/Exporter.hpp
index 692830f02..fb890129e 100644
--- a/include/assimp/Exporter.hpp
+++ b/include/assimp/Exporter.hpp
@@ -348,16 +348,14 @@ public:
 	 *   are defined in the aiConfig.g header (all constants share the
 	 *   prefix AI_CONFIG_XXX and are simple strings).
 	 * @param iValue New value of the property
-	 * @param bWasExisting Optional pointer to receive true if the
-	 *   property was set before. The new value replaces the previous value
-	 *   in this case.
+	 * @return true if the property was set before. The new value replaces
+	 *   the previous value in this case.
 	 * @note Property of different types (float, int, string ..) are kept
 	 *   on different stacks, so calling SetPropertyInteger() for a 
 	 *   floating-point property has no effect - the loader will call
 	 *   GetPropertyFloat() to read the property, but it won't be there.
 	 */
-	void SetPropertyInteger(const char* szName, int iValue, 
-		bool* bWasExisting = NULL);
+	bool SetPropertyInteger(const char* szName, int iValue);
 
 	// -------------------------------------------------------------------
 	/** Set a boolean configuration property. Boolean properties
@@ -366,30 +364,27 @@ public:
 	 *  #GetPropertyBool and vice versa.
 	 * @see SetPropertyInteger()
 	 */
-	void SetPropertyBool(const char* szName, bool value, bool* bWasExisting = NULL)	{
-		SetPropertyInteger(szName,value,bWasExisting);
+	bool SetPropertyBool(const char* szName, bool value)	{
+		return SetPropertyInteger(szName,value);
 	}
 
 	// -------------------------------------------------------------------
 	/** Set a floating-point configuration property.
 	 * @see SetPropertyInteger()
 	 */
-	void SetPropertyFloat(const char* szName, float fValue, 
-		bool* bWasExisting = NULL);
+	bool SetPropertyFloat(const char* szName, float fValue);
 
 	// -------------------------------------------------------------------
 	/** Set a string configuration property.
 	 * @see SetPropertyInteger()
 	 */
-	void SetPropertyString(const char* szName, const std::string& sValue, 
-		bool* bWasExisting = NULL);
+	bool SetPropertyString(const char* szName, const std::string& sValue);
 
 	// -------------------------------------------------------------------
 	/** Set a matrix configuration property.
 	 * @see SetPropertyInteger()
 	 */
-	void SetPropertyMatrix(const char* szName, const aiMatrix4x4& sValue, 
-		bool* bWasExisting = NULL);
+	bool SetPropertyMatrix(const char* szName, const aiMatrix4x4& sValue);
 
 	// -------------------------------------------------------------------
 	/** Get a configuration property.
diff --git a/include/assimp/Importer.hpp b/include/assimp/Importer.hpp
index 8aa9e5ae5..8d9141aeb 100644
--- a/include/assimp/Importer.hpp
+++ b/include/assimp/Importer.hpp
@@ -194,16 +194,14 @@ public:
 	 *   are defined in the aiConfig.g header (all constants share the
 	 *   prefix AI_CONFIG_XXX and are simple strings).
 	 * @param iValue New value of the property
-	 * @param bWasExisting Optional pointer to receive true if the
-	 *   property was set before. The new value replaces the previous value
-	 *   in this case.
+	 * @return true if the property was set before. The new value replaces
+	 *   the previous value in this case.
 	 * @note Property of different types (float, int, string ..) are kept
 	 *   on different stacks, so calling SetPropertyInteger() for a 
 	 *   floating-point property has no effect - the loader will call
 	 *   GetPropertyFloat() to read the property, but it won't be there.
 	 */
-	void SetPropertyInteger(const char* szName, int iValue, 
-		bool* bWasExisting = NULL);
+	bool SetPropertyInteger(const char* szName, int iValue);
 
 	// -------------------------------------------------------------------
 	/** Set a boolean configuration property. Boolean properties
@@ -212,30 +210,27 @@ public:
 	 *  #GetPropertyBool and vice versa.
 	 * @see SetPropertyInteger()
 	 */
-	void SetPropertyBool(const char* szName, bool value, bool* bWasExisting = NULL)	{
-		SetPropertyInteger(szName,value,bWasExisting);
+	bool SetPropertyBool(const char* szName, bool value)	{
+		return SetPropertyInteger(szName,value);
 	}
 
 	// -------------------------------------------------------------------
 	/** Set a floating-point configuration property.
 	 * @see SetPropertyInteger()
 	 */
-	void SetPropertyFloat(const char* szName, float fValue, 
-		bool* bWasExisting = NULL);
+	bool SetPropertyFloat(const char* szName, float fValue);
 
 	// -------------------------------------------------------------------
 	/** Set a string configuration property.
 	 * @see SetPropertyInteger()
 	 */
-	void SetPropertyString(const char* szName, const std::string& sValue, 
-		bool* bWasExisting = NULL);
+	bool SetPropertyString(const char* szName, const std::string& sValue);
 
 	// -------------------------------------------------------------------
 	/** Set a matrix configuration property.
 	 * @see SetPropertyInteger()
 	 */
-	void SetPropertyMatrix(const char* szName, const aiMatrix4x4& sValue, 
-		bool* bWasExisting = NULL);
+	bool SetPropertyMatrix(const char* szName, const aiMatrix4x4& sValue);
 
 	// -------------------------------------------------------------------
 	/** Get a configuration property.