diff --git a/libgnucash/engine/CMakeLists.txt b/libgnucash/engine/CMakeLists.txt
index 202d9102544..599fcc0077e 100644
--- a/libgnucash/engine/CMakeLists.txt
+++ b/libgnucash/engine/CMakeLists.txt
@@ -6,7 +6,7 @@ add_subdirectory(mocks)
 
 set(engine_noinst_HEADERS
   AccountP.hpp
-  SplitP.h
+  SplitP.hpp
   SX-book.h
   SX-ttinfo.h
   TransactionP.hpp
diff --git a/libgnucash/engine/SplitP.h b/libgnucash/engine/SplitP.hpp
similarity index 99%
rename from libgnucash/engine/SplitP.h
rename to libgnucash/engine/SplitP.hpp
index 4192cc5dde1..d13c2ffa1bf 100644
--- a/libgnucash/engine/SplitP.h
+++ b/libgnucash/engine/SplitP.hpp
@@ -1,5 +1,5 @@
 /********************************************************************\
- * SplitP.h -- private header for splits                            *
+ * SplitP.hpp -- private header for splits                            *
  * Copyright (C) 1997 Robin D. Clark                                *
  * Copyright (C) 1997-2000 Linas Vepstas <linas@linas.org>          *
  * Copyright (C) 2000 Bill Gribble                                  *
@@ -25,7 +25,7 @@
 
 /*
  * FILE:
- * SplitP.h
+ * SplitP.hpp
  *
  * FUNCTION:
  * The is the *private* split header file.  Code outside of
diff --git a/libgnucash/engine/Transaction.cpp b/libgnucash/engine/Transaction.cpp
index 0cc0fcf4aad..dc6d5186bd8 100644
--- a/libgnucash/engine/Transaction.cpp
+++ b/libgnucash/engine/Transaction.cpp
@@ -46,7 +46,7 @@
 #include "Scrub.h"
 #include "Scrub3.h"
 #include "TransactionP.hpp"
-#include "SplitP.h"
+#include "SplitP.hpp"
 #include "TransLog.h"
 #include "cap-gains.h"
 #include "gnc-commodity.h"
diff --git a/libgnucash/engine/TransactionP.hpp b/libgnucash/engine/TransactionP.hpp
index 50a2d80a878..512e5dde017 100644
--- a/libgnucash/engine/TransactionP.hpp
+++ b/libgnucash/engine/TransactionP.hpp
@@ -49,7 +49,7 @@
 #include <glib.h>
 
 #include "gnc-engine.h"   /* for typedefs */
-#include "SplitP.h"
+#include "SplitP.hpp"
 #include "qof.h"
 
 
diff --git a/libgnucash/engine/mocks/gmock-Split.h b/libgnucash/engine/mocks/gmock-Split.h
index ce022fb2d00..0fe7eb24e41 100644
--- a/libgnucash/engine/mocks/gmock-Split.h
+++ b/libgnucash/engine/mocks/gmock-Split.h
@@ -4,7 +4,7 @@
 #include <gmock/gmock.h>
 
 #include <Split.h>
-#include <SplitP.h>
+#include <SplitP.hpp>
 
 #include "gmock-qofbook.h"
 #include "gmock-gobject.h"
diff --git a/libgnucash/engine/test/utest-Split.cpp b/libgnucash/engine/test/utest-Split.cpp
index 23d163ee597..8ec6d59399e 100644
--- a/libgnucash/engine/test/utest-Split.cpp
+++ b/libgnucash/engine/test/utest-Split.cpp
@@ -28,7 +28,7 @@
 #include <unittest-support.h>
 /* Add specific headers for this class */
 #include <Split.h>
-#include <SplitP.h>
+#include <SplitP.hpp>
 #include <Account.h>
 #include <Transaction.h>
 #include <TransactionP.hpp>