diff --git a/kernel/mips64/zsum.S b/kernel/mips64/zsum.S
index 129b97900..f6da793de 100644
--- a/kernel/mips64/zsum.S
+++ b/kernel/mips64/zsum.S
@@ -73,6 +73,8 @@
 	MTC	$0,  s1
 
 	MTC	$0,  s2
+
+	blez    INCX, .L999
 	dsll	INCX, INCX, ZBASE_SHIFT
 
 	blez	N, .L999