diff --git a/tests/Makefile.am b/tests/Makefile.am
index 46db97225..c3e2dc570 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -8,10 +8,10 @@ else
 test_up_PLIB_LIBS = -lplibsg -lplibul
 endif
 
-est_epsilon_SOURCES = est-epsilon.c
+est_epsilon_SOURCES = est-epsilon.cxx
 est_epsilon_LDADD =  $(opengl_LIBS)
 
-gl_info_SOURCES = gl-info.c
+gl_info_SOURCES = gl-info.cxx
 gl_info_LDADD = $(opengl_LIBS)
 
 al_info_SOURCES = al-info.c
diff --git a/tests/est-epsilon.c b/tests/est-epsilon.cxx
similarity index 100%
rename from tests/est-epsilon.c
rename to tests/est-epsilon.cxx
diff --git a/tests/gl-info.c b/tests/gl-info.cxx
similarity index 100%
rename from tests/gl-info.c
rename to tests/gl-info.cxx