diff --git a/rules.mk b/rules.mk
index 96a54c9fe..a4dcaa1fc 100644
--- a/rules.mk
+++ b/rules.mk
@@ -106,9 +106,9 @@ ifneq ($(CONFIG_LARGEFILE),y)
 endif
 
 ifeq ($(CONFIG_TAR_VERBOSITY),y)
-  TAR_OPTIONS=-xvf -
+  TAR_OPTIONS:=-xvf -
 else
-  TAR_OPTIONS=-xf -
+  TAR_OPTIONS:=-xf -
 endif
 
 all: