diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index da613eb..359f678 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -341,6 +341,7 @@
 
 config MIPS_OPTIMIZED_STRING_FUNCTIONS
 	bool "use assembler optimized string functions"
+	depends on !64BIT
 	default y
 	help
 	  Say yes here to use assembler optimized memcpy / memset functions.