diff --git a/day2/Makefile b/day2/Makefile
index c74f2bc..e7c6d10 100644
--- a/day2/Makefile
+++ b/day2/Makefile
@@ -10,6 +10,6 @@ all: $(BIN_NAME)
 clean:
 	rm -f $(BIN_NAME)
 
-$(BIN_NAME):
+$(BIN_NAME): day2.cpp
 	$(CC) $(CCFLAGS) $(LDFLAGS) day2.cpp
 
diff --git a/day3/Makefile b/day3/Makefile
index 0e6b451..6ffafab 100644
--- a/day3/Makefile
+++ b/day3/Makefile
@@ -10,6 +10,6 @@ all: $(BIN_NAME)
 clean:
 	rm -f $(BIN_NAME)
 
-$(BIN_NAME):
+$(BIN_NAME): day3.cpp
 	$(CC) $(CCFLAGS) $(LDFLAGS) day3.cpp