diff --git a/blake2b/blake2b_amd64.s b/blake2b/blake2b_amd64.s
index 3017cf0..7a876ba 100644
--- a/blake2b/blake2b_amd64.s
+++ b/blake2b/blake2b_amd64.s
@@ -269,7 +269,7 @@ noinc:
 TEXT ·supportSSE4(SB), 4, $0-1
 	MOVL $1, AX
 	CPUID
-	SHRL $15, CX  // Bit 15 indicates SSE4 support
+	SHRL $19, CX  // Bit 19 indicates SSE4 support
 	ANDL $1, CX  // CX != 0 if support SSE4
 	MOVB CX, ret+0(FP)
 	RET