diff --git a/libsrc/Makefile.am b/libsrc/Makefile.am
index b7d60ee9..1f068874 100644
--- a/libsrc/Makefile.am
+++ b/libsrc/Makefile.am
@@ -31,7 +31,7 @@ SUBDIRS = \
 
 lib_LTLIBRARIES = libvips.la
 
-libvips_la_SOURCES = dummy.c dummy2.cpp
+libvips_la_SOURCES = dummy.c dummy2.cc
 
 # DLLs need dependant libs there too ... put @VIPS_LIBS@ at the end
 libvips_la_LIBADD = \
diff --git a/libsrc/dummy2.cpp b/libsrc/dummy.cc
similarity index 100%
rename from libsrc/dummy2.cpp
rename to libsrc/dummy.cc