diff --git a/java/system_modules.go b/java/system_modules.go
index 73a5131..d98e0ab 100644
--- a/java/system_modules.go
+++ b/java/system_modules.go
@@ -134,6 +134,7 @@
 			fmt.Fprintln(w, makevar, ":=", system.outputFile.String())
 			fmt.Fprintln(w, ".KATI_READONLY", ":=", makevar)
 			fmt.Fprintln(w, name+":", "$("+makevar+")")
+			fmt.Fprintln(w, ".PHONY:", name)
 			fmt.Fprintln(w)
 			makevar = "SOONG_SYSTEM_MODULES_LIBS_" + name
 			fmt.Fprintln(w, makevar, ":=", strings.Join(system.properties.Libs, " "))