diff --git a/doc/reference/using-cpp.xml b/doc/reference/using-cpp.xml
index f26a504f..5400f478 100644
--- a/doc/reference/using-cpp.xml
+++ b/doc/reference/using-cpp.xml
@@ -287,23 +287,23 @@ main( int argc, char **argv )
     <title>Extending the C++ interface</title>
 
     <para>
-			The C++ interface comes in two parts. First, VImage8.h defines a simple 
-			layer over #GObject for automatic reference counting, then a generic way 
-			to call any vips8 operation with VImage::call(), then a few convenience 
-			functions, then a set of overloads.
+      The C++ interface comes in two parts. First, VImage8.h defines a simple 
+      layer over #GObject for automatic reference counting, then a generic way 
+      to call any vips8 operation with VImage::call(), then a few convenience 
+      functions, then a set of overloads.
     </para>
 
     <para>
-			The member function for each operation, for example VImage::add(), is 
-			generated by a small Python program called <code>gen-operators.py</code>,
-			and its companion, <code>gen-operators-h.py</code> to generate the 
-			headers. If you write a new VIPS operator, you'll need to rerun these 
-			programs to make the new member function. 
+      The member function for each operation, for example VImage::add(), is 
+      generated by a small Python program called <code>gen-operators.py</code>,
+      and its companion, <code>gen-operators-h.py</code> to generate the 
+      headers. If you write a new VIPS operator, you'll need to rerun these 
+      programs to make the new member function. 
     </para>
 
-		<para>
-			You can write the wrapper yourself, of course, they are very simple. 
-			The one for VImage::add() looks like this:
+    <para>
+      You can write the wrapper yourself, of course, they are very simple. 
+      The one for VImage::add() looks like this:
 
 <programlisting language="C++">
 VImage VImage::add(VImage right, VOption *options)
@@ -317,11 +317,11 @@ VImage VImage::add(VImage right, VOption *options)
       set("left", *this) ->
       set("right", right));
 
-	return out;
+  return out;
 }
 </programlisting>
 
-			Where VImage::call() is the generic call-a-vips8-operation function.
+      Where VImage::call() is the generic call-a-vips8-operation function.
     </para>
   </refsect1>
 </refentry>