diff --git a/eo/app/mastermind/Makefile.am b/eo/app/mastermind/Makefile.am
index 621733f0..d43be627 100644
--- a/eo/app/mastermind/Makefile.am
+++ b/eo/app/mastermind/Makefile.am
@@ -17,7 +17,7 @@ bin_PROGRAMS = mastermind
 
 ###############################################################################
 
-mastermind_SOURCES = mastermind.cc
+mastermind_SOURCES = mastermind.cpp
 mastermind_DEPENDENCIES = $(DEPS)
 mastermind_LDFLAGS = -lm
 mastermind_LDADD = $(LDADDS)
diff --git a/eo/app/mastermind/mastermind.cc b/eo/app/mastermind/mastermind.cpp
similarity index 100%
rename from eo/app/mastermind/mastermind.cc
rename to eo/app/mastermind/mastermind.cpp