diff --git a/compiler/cpp/Makefile.am b/compiler/cpp/Makefile.am
index 6f618ea..6061988 100644
--- a/compiler/cpp/Makefile.am
+++ b/compiler/cpp/Makefile.am
@@ -10,7 +10,6 @@
                  src/md5c.c \
                  src/generate/t_generator.cc \
                  src/generate/t_php_generator.cc \
-                 src/generate/t_rb_generator.cc \
                  src/generate/t_xsd_generator.cc \
                  src/generate/t_perl_generator.cc \
                  src/generate/t_erl_generator.cc \
@@ -55,6 +54,9 @@
 if THRIFT_GEN_py
 thrift_SOURCES += src/generate/t_py_generator.cc
 endif
+if THRIFT_GEN_rb
+thrift_SOURCES += src/generate/t_rb_generator.cc
+endif
 if THRIFT_GEN_cocoa
 thrift_SOURCES += src/generate/t_cocoa_generator.cc
 endif