diff --git a/libgnucash/engine/CMakeLists.txt b/libgnucash/engine/CMakeLists.txt
index ccf292bdfb..f07e022e64 100644
--- a/libgnucash/engine/CMakeLists.txt
+++ b/libgnucash/engine/CMakeLists.txt
@@ -158,7 +158,7 @@ set (engine_SOURCES
   gnc-commodity.cpp
   gnc-date.cpp
   gnc-datetime.cpp
-  gnc-engine.c
+  gnc-engine.cpp
   gnc-euro.c
   gnc-event.c
   gnc-features.cpp
diff --git a/libgnucash/engine/gnc-engine.c b/libgnucash/engine/gnc-engine.cpp
similarity index 97%
rename from libgnucash/engine/gnc-engine.c
rename to libgnucash/engine/gnc-engine.cpp
index a8d665bddd..f472dc5e92 100644
--- a/libgnucash/engine/gnc-engine.c
+++ b/libgnucash/engine/gnc-engine.cpp
@@ -40,7 +40,7 @@
 /* gnc-backend-file location */
 #include "gnc-path.h"
 
-static GList * engine_init_hooks = NULL;
+static GList * engine_init_hooks = nullptr;
 static int engine_is_initialized = 0;
 
 EngineCommitErrorCallback g_error_cb;
@@ -77,7 +77,7 @@ gnc_engine_init_part2()
         { "", "gncmod-backend-dbi", TRUE },
 #endif
         { "", "gncmod-backend-xml", TRUE },
-        { NULL, NULL, FALSE }
+        { nullptr, nullptr, FALSE }
     }, *lib;
 
     for (lib = libs; lib->lib ; lib++)
@@ -172,7 +172,7 @@ gnc_engine_add_commit_error_callback( EngineCommitErrorCallback cb, gpointer dat
 void
 gnc_engine_signal_commit_error( QofBackendError errcode )
 {
-    if ( g_error_cb != NULL )
+    if ( g_error_cb != nullptr )
     {
         (*g_error_cb)( g_error_cb_data, errcode );
     }
diff --git a/po/POTFILES.in b/po/POTFILES.in
index 25b32a4050..bc28fad43c 100644
--- a/po/POTFILES.in
+++ b/po/POTFILES.in
@@ -638,7 +638,7 @@ libgnucash/engine/gncCustomer.c
 libgnucash/engine/gnc-date.cpp
 libgnucash/engine/gnc-datetime.cpp
 libgnucash/engine/gncEmployee.c
-libgnucash/engine/gnc-engine.c
+libgnucash/engine/gnc-engine.cpp
 libgnucash/engine/gncEntry.c
 libgnucash/engine/gnc-euro.c
 libgnucash/engine/gnc-event.c