diff --git a/lib/string.c b/lib/string.c
index dc4a863..3a03782 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -785,12 +785,24 @@
 	if (bytes <= 16)
 		return check_bytes8(start, value, bytes);
 
-	value64 = value | value << 8 | value << 16 | value << 24;
-	value64 = (value64 & 0xffffffff) | value64 << 32;
-	prefix = 8 - ((unsigned long)start) % 8;
+	value64 = value;
+#if defined(ARCH_HAS_FAST_MULTIPLIER) && BITS_PER_LONG == 64
+	value64 *= 0x0101010101010101;
+#elif defined(ARCH_HAS_FAST_MULTIPLIER)
+	value64 *= 0x01010101;
+	value64 |= value64 << 32;
+#else
+	value64 |= value64 << 8;
+	value64 |= value64 << 16;
+	value64 |= value64 << 32;
+#endif
 
+	prefix = (unsigned long)start % 8;
 	if (prefix) {
-		u8 *r = check_bytes8(start, value, prefix);
+		u8 *r;
+
+		prefix = 8 - prefix;
+		r = check_bytes8(start, value, prefix);
 		if (r)
 			return r;
 		start += prefix;