diff --git a/cplusplus/VImage.cpp b/cplusplus/VImage.cpp
index 01e1a6f3..a40e7418 100644
--- a/cplusplus/VImage.cpp
+++ b/cplusplus/VImage.cpp
@@ -64,7 +64,7 @@ to_vectorv( int n, ... )
 	va_list ap;
 
 	va_start( ap, n );
-	for( int i = 0; i < n; i++ )
+	for( std::vector<double>::size_type i = 0; i < size_t(n); i++ )
 		vector[i] = va_arg( ap, double );
 	va_end( ap );
 
@@ -82,7 +82,7 @@ to_vector( int n, double array[] )
 {
 	std::vector<double> vector( n );
 
-	for( int i = 0; i < n; i++ )
+	for( std::vector<double>::size_type i = 0; i < size_t(n); i++ )
 		vector[i] = array[i];
 
 	return( vector );
@@ -93,7 +93,7 @@ negate( std::vector<double> vector )
 {
 	std::vector<double> new_vector( vector.size() );
 
-	for( unsigned int i = 0; i < vector.size(); i++ )
+	for( std::vector<double>::size_type i = 0; i < vector.size(); i++ )
 		new_vector[i] = vector[i] * -1;
 
 	return( new_vector );
@@ -104,7 +104,7 @@ invert( std::vector<double> vector )
 {
 	std::vector<double> new_vector( vector.size() );
 
-	for( unsigned int i = 0; i < vector.size(); i++ )
+	for( std::vector<double>::size_type i = 0; i < vector.size(); i++ )
 		new_vector[i] = 1.0 / vector[i];
 
 	return( new_vector );
@@ -210,7 +210,6 @@ VOption::set( const char *name, std::vector<int> value )
 	Pair *pair = new Pair( name );
 
 	int *array;
-	unsigned int i;
 
 	pair->input = true;
 
@@ -219,7 +218,7 @@ VOption::set( const char *name, std::vector<int> value )
 		static_cast< int >( value.size() ) );
 	array = vips_value_get_array_int( &pair->value, NULL );
 
-	for( i = 0; i < value.size(); i++ ) 
+	for( std::vector<double>::size_type i = 0; i < value.size(); i++ ) 
 		array[i] = value[i];
 
 	options.push_back( pair );
@@ -234,7 +233,6 @@ VOption::set( const char *name, std::vector<double> value )
 	Pair *pair = new Pair( name );
 
 	double *array;
-	unsigned int i;
 
 	pair->input = true;
 
@@ -243,7 +241,7 @@ VOption::set( const char *name, std::vector<double> value )
 		static_cast< int >( value.size() ) );
 	array = vips_value_get_array_double( &pair->value, NULL );
 
-	for( i = 0; i < value.size(); i++ ) 
+	for( std::vector<double>::size_type i = 0; i < value.size(); i++ ) 
 		array[i] = value[i];
 
 	options.push_back( pair );
@@ -258,7 +256,6 @@ VOption::set( const char *name, std::vector<VImage> value )
 	Pair *pair = new Pair( name );
 
 	VipsImage **array;
-	unsigned int i;
 
 	pair->input = true;
 
@@ -267,7 +264,7 @@ VOption::set( const char *name, std::vector<VImage> value )
 		static_cast< int >( value.size() ) );
 	array = vips_value_get_array_image( &pair->value, NULL );
 
-	for( i = 0; i < value.size(); i++ ) {
+	for( std::vector<double>::size_type i = 0; i < value.size(); i++ ) {
 		VipsImage *vips_image = value[i].get_image();
 
 		array[i] = vips_image;
@@ -488,10 +485,8 @@ VOption::get_operation( VipsOperation *operation )
 				double *array =
 					vips_value_get_array_double( value,
 					&length );
-				int j;
-
 				((*i)->vvector)->resize( length );
-				for( j = 0; j < length; j++ )
+				for( size_t j = 0; j < length; j++ )
 					(*((*i)->vvector))[j] = array[j];
 			}
 			else if( type == VIPS_TYPE_BLOB ) {