diff --git a/impls/sml/Makefile b/impls/sml/Makefile
index 4964ab04..b61b2def 100644
--- a/impls/sml/Makefile
+++ b/impls/sml/Makefile
@@ -5,7 +5,7 @@ all: $(STEP_BINS)
 step0_repl: step0_repl.mlb step0_repl.sml main.sml
 	mlton -output $@ $<
 
-step1_read_print: step1_read_print.mlb step1_read_print.sml reader.sml printer.sml types.sml util.sml
+step1_read_print: step1_read_print.mlb step1_read_print.sml reader.sml printer.sml types.sml util.sml main.sml
 	mlton -output $@ $<
 
 clean: