diff --git a/Makefile.am b/Makefile.am
index 63bfae38..dc192954 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -179,6 +179,7 @@ clean-local:
 
 ledger_so_SOURCES = \
 	src/pyledger.cc \
+	src/pyinterp.cc \
 	src/py_utils.cc \
 	src/py_times.cc \
 	src/py_commodity.cc \