--- a/nbproject/project.xml	Tue Dec 04 15:20:03 2018 +0100
+++ b/nbproject/project.xml	Tue Dec 04 17:19:10 2018 +0100
@@ -45,7 +45,7 @@
             <name>relpipe-out-nullbyte.cpp</name>
             <c-extensions/>
             <cpp-extensions>cpp</cpp-extensions>
-            <header-extensions/>
+            <header-extensions>h</header-extensions>
             <sourceEncoding>UTF-8</sourceEncoding>
             <sourceRootList>
                 <sourceRootElem>.</sourceRootElem>