diff --git a/c/mapping/Makefile.am b/c/mapping/Makefile.am
index 45211319d..cddf2b3b2 100644
--- a/c/mapping/Makefile.am
+++ b/c/mapping/Makefile.am
@@ -35,6 +35,7 @@ libmapping_la_SOURCES=	\
 			mapper_uniq.c \
 			mappers.h \
 			mlr_dsl_cst.h \
+			mlr_dsl_cst.c \
 			stats1_accumulators.c \
 			stats1_accumulators.h
 libmapping_la_LIBADD=	../lib/libmlr.la ../cli/libcli.la ../input/libinput.la