diff --git a/vp8/vp8cx.mk b/vp8/vp8cx.mk
index 670c02280..8f0681fb9 100644
--- a/vp8/vp8cx.mk
+++ b/vp8/vp8cx.mk
@@ -116,7 +116,7 @@ VP8_CX_SRCS-$(HAVE_SSSE3) += encoder/x86/quantize_ssse3.asm
 VP8_CX_SRCS-$(HAVE_SSE4_1) += encoder/x86/sad_sse4.asm
 VP8_CX_SRCS-$(ARCH_X86)$(ARCH_X86_64) += encoder/x86/quantize_mmx.asm
 VP8_CX_SRCS-$(ARCH_X86)$(ARCH_X86_64) += encoder/x86/encodeopt.asm
-VP8_CX_SRCS-$(ARCH_X86)$(ARCH_X86_64) += encoder/x86/ssim_opt.asm
+VP8_CX_SRCS-$(ARCH_X86_64) += encoder/x86/ssim_opt.asm
 
 ifeq ($(CONFIG_REALTIME_ONLY),yes)
 VP8_CX_SRCS_REMOVE-$(HAVE_SSE2) += encoder/x86/temporal_filter_apply_sse2.asm