Do not store read makefiles if --use_cache is not specified
diff --git a/eval.go b/eval.go
index 52e6c13..45eb203 100644
--- a/eval.go
+++ b/eval.go
@@ -262,6 +262,10 @@
 }
 
 func (ev *Evaluator) updateReadMakefile(fn string, c []byte, st int32) {
+	if !useCache {
+		return
+	}
+
 	rm, present := ev.readMks[fn]
 	if present {
 		switch rm.State {