diff --git a/src/include/port/pg_utf8.h b/src/include/port/pg_utf8.h
index dac2afc130..a0c94dd4f3 100644
--- a/src/include/port/pg_utf8.h
+++ b/src/include/port/pg_utf8.h
@@ -53,26 +53,25 @@ extern int pg_validate_utf8_fallback(const unsigned char *s, int len);
 static inline int
 check_ascii(const unsigned char *s, int len)
 {
-	uint64		half1, half2,
+	uint64		chunk,
 				highbit_mask;
 
-	if  (len >= 2 * sizeof(uint64))
+	if  (len >= sizeof(uint64))
 	{
-		memcpy(&half1, s, sizeof(uint64));
-		memcpy(&half2, s + sizeof(uint64), sizeof(uint64));
+		memcpy(&chunk, s, sizeof(uint64));
 
 		/*
 		 * If there are any zero bytes, bail and let the slow
 		 * path handle it.
 		 */
-		if (HAS_ZERO(half1) || HAS_ZERO(half2))
+		if (HAS_ZERO(chunk))
 			return 0;
 
 		/* Check if any bytes in this chunk have the high bit set. */
-		highbit_mask = ((half1 | half2) & UINT64CONST(0x8080808080808080));
+		highbit_mask = (chunk & UINT64CONST(0x8080808080808080));
 
 		if (!highbit_mask)
-			return 2 * sizeof(uint64);
+			return sizeof(uint64);
 		else
 			return 0;
 	}