diff --git a/lib/dns/rbtdb.c b/lib/dns/rbtdb.c
index 6eed090f66..4efa16bead 100644
--- a/lib/dns/rbtdb.c
+++ b/lib/dns/rbtdb.c
@@ -9848,7 +9848,7 @@ setownercase(rdatasetheader_t *header, const dns_name_t *name) {
 	memset(header->upper, 0, sizeof(header->upper));
 	fully_lower = true;
 	for (i = 0; i < name->length; i++) {
-		if (name->ndata[i] >= 0x41 && name->ndata[i] <= 0x5a) {
+		if (name->ndata[i] >= 'A' && name->ndata[i] <= 'Z') {
 			{
 				header->upper[i / 8] |= 1 << (i % 8);
 				fully_lower = false;
@@ -9877,54 +9877,20 @@ rdataset_setownercase(dns_rdataset_t *rdataset, const dns_name_t *name) {
 		    isc_rwlocktype_write);
 }
 
-static const unsigned char charmask[] = {
-	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-	0x00, 0x00, 0x00, 0x00, 0x00, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20,
-	0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20,
-	0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x00, 0x00, 0x00, 0x00, 0x00,
-	0x00, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20,
-	0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20,
-	0x20, 0x20, 0x20, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-	0x00, 0x00, 0x00, 0x00
+static const unsigned char maptolower[256] = {
+	['A'] = 'a', ['B'] = 'b', ['C'] = 'c', ['D'] = 'd', ['E'] = 'e',
+	['F'] = 'f', ['G'] = 'g', ['H'] = 'h', ['I'] = 'i', ['J'] = 'j',
+	['K'] = 'k', ['L'] = 'l', ['M'] = 'm', ['N'] = 'n', ['O'] = 'o',
+	['P'] = 'p', ['Q'] = 'q', ['R'] = 'r', ['S'] = 's', ['T'] = 't',
+	['U'] = 'u', ['V'] = 'v', ['X'] = 'x', ['Y'] = 'y', ['Z'] = 'z',
 };
 
-static const unsigned char maptolower[] = {
-	0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b,
-	0x0c, 0x0d, 0x0e, 0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
-	0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 0x20, 0x21, 0x22, 0x23,
-	0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f,
-	0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3a, 0x3b,
-	0x3c, 0x3d, 0x3e, 0x3f, 0x40, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67,
-	0x68, 0x69, 0x6a, 0x6b, 0x6c, 0x6d, 0x6e, 0x6f, 0x70, 0x71, 0x72, 0x73,
-	0x74, 0x75, 0x76, 0x77, 0x78, 0x79, 0x7a, 0x5b, 0x5c, 0x5d, 0x5e, 0x5f,
-	0x60, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69, 0x6a, 0x6b,
-	0x6c, 0x6d, 0x6e, 0x6f, 0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77,
-	0x78, 0x79, 0x7a, 0x7b, 0x7c, 0x7d, 0x7e, 0x7f, 0x80, 0x81, 0x82, 0x83,
-	0x84, 0x85, 0x86, 0x87, 0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x8d, 0x8e, 0x8f,
-	0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97, 0x98, 0x99, 0x9a, 0x9b,
-	0x9c, 0x9d, 0x9e, 0x9f, 0xa0, 0xa1, 0xa2, 0xa3, 0xa4, 0xa5, 0xa6, 0xa7,
-	0xa8, 0xa9, 0xaa, 0xab, 0xac, 0xad, 0xae, 0xaf, 0xb0, 0xb1, 0xb2, 0xb3,
-	0xb4, 0xb5, 0xb6, 0xb7, 0xb8, 0xb9, 0xba, 0xbb, 0xbc, 0xbd, 0xbe, 0xbf,
-	0xc0, 0xc1, 0xc2, 0xc3, 0xc4, 0xc5, 0xc6, 0xc7, 0xc8, 0xc9, 0xca, 0xcb,
-	0xcc, 0xcd, 0xce, 0xcf, 0xd0, 0xd1, 0xd2, 0xd3, 0xd4, 0xd5, 0xd6, 0xd7,
-	0xd8, 0xd9, 0xda, 0xdb, 0xdc, 0xdd, 0xde, 0xdf, 0xe0, 0xe1, 0xe2, 0xe3,
-	0xe4, 0xe5, 0xe6, 0xe7, 0xe8, 0xe9, 0xea, 0xeb, 0xec, 0xed, 0xee, 0xef,
-	0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8, 0xf9, 0xfa, 0xfb,
-	0xfc, 0xfd, 0xfe, 0xff
+static const unsigned char maptoupper[256] = {
+	['a'] = 'A', ['b'] = 'B', ['c'] = 'C', ['d'] = 'D', ['e'] = 'E',
+	['f'] = 'F', ['g'] = 'G', ['h'] = 'H', ['i'] = 'I', ['j'] = 'J',
+	['k'] = 'K', ['l'] = 'L', ['m'] = 'M', ['n'] = 'N', ['o'] = 'O',
+	['p'] = 'P', ['q'] = 'Q', ['r'] = 'R', ['s'] = 'S', ['t'] = 'T',
+	['u'] = 'U', ['v'] = 'V', ['x'] = 'X', ['y'] = 'Y', ['z'] = 'Z',
 };
 
 static void
@@ -9932,10 +9898,9 @@ rdataset_getownercase(const dns_rdataset_t *rdataset, dns_name_t *name) {
 	dns_rbtdb_t *rbtdb = rdataset->private1;
 	dns_rbtnode_t *rbtnode = rdataset->private2;
 	unsigned char *raw = rdataset->private3; /* RDATASLAB */
-	rdatasetheader_t *header;
-	unsigned int i, j;
-	unsigned char bits;
-	unsigned char c, flip;
+	rdatasetheader_t *header = NULL;
+	uint8_t mask = (1 << 7);
+	uint8_t bits = 0;
 
 	header = (struct rdatasetheader *)(raw - sizeof(*header));
 
@@ -9946,85 +9911,36 @@ rdataset_getownercase(const dns_rdataset_t *rdataset, dns_name_t *name) {
 		goto unlock;
 	}
 
-#if 0
-	/*
-	 * This was the original code, and is implemented differently in
-	 * the #else block that follows.
-	 */
-	for (i = 0; i < name->length; i++) {
-		/*
-		 * Set the case bit if it does not match the recorded bit.
-		 */
-		if (name->ndata[i] >= 0x61 && name->ndata[i] <= 0x7a &&
-		    (header->upper[i / 8] & (1 << (i % 8))) != 0)
-		{
-			name->ndata[i] &= ~0x20; /* clear the lower case bit */
-		} else if (name->ndata[i] >= 0x41 && name->ndata[i] <= 0x5a &&
-			   (header->upper[i / 8] & (1 << (i % 8))) == 0)
-		{
-			name->ndata[i] |= 0x20; /* set the lower case bit */
-		}
-	}
-#else  /* if 0 */
-
 	if (ISC_LIKELY(CASEFULLYLOWER(header))) {
-		unsigned char *bp, *be;
-		bp = name->ndata;
-		be = bp + name->length;
-
-		while (bp <= be - 4) {
-			c = bp[0];
-			bp[0] = maptolower[c];
-			c = bp[1];
-			bp[1] = maptolower[c];
-			c = bp[2];
-			bp[2] = maptolower[c];
-			c = bp[3];
-			bp[3] = maptolower[c];
-			bp += 4;
+		for (size_t i = 0; i < name->length; i++) {
+			uint8_t c = name->ndata[i];
+			if (c >= 'A' && c <= 'Z') {
+				name->ndata[i] = maptolower[c];
+			}
 		}
-		while (bp < be) {
-			c = *bp;
-			*bp++ = maptolower[c];
-		}
-		goto unlock;
-	}
+	} else {
+		for (size_t i = 0; i < name->length; i++) {
+			uint8_t c = name->ndata[i];
 
-	i = 0;
-	for (j = 0; j < (name->length >> 3); j++) {
-		unsigned int k;
+			if (mask == (1 << 7)) {
+				bits = header->upper[i / 8];
+				mask = 1;
+			} else {
+				mask <<= 1;
+			}
 
-		bits = ~(header->upper[j]);
-
-		for (k = 0; k < 8; k++) {
-			c = name->ndata[i];
-			flip = (bits & 1) << 5;
-			flip ^= c;
-			flip &= charmask[c];
-			name->ndata[i] ^= flip;
-
-			i++;
-			bits >>= 1;
+			if (c >= 'a' && c <= 'z') {
+				if ((bits & mask) != 0) {
+					name->ndata[i] = maptoupper[c];
+				}
+			} else if (c >= 'A' && c <= 'Z') {
+				if ((bits & mask) == 0) {
+					name->ndata[i] = maptolower[c];
+				}
+			}
 		}
 	}
 
-	if (ISC_UNLIKELY(i == name->length)) {
-		goto unlock;
-	}
-
-	bits = ~(header->upper[j]);
-
-	for (; i < name->length; i++) {
-		c = name->ndata[i];
-		flip = (bits & 1) << 5;
-		flip ^= c;
-		flip &= charmask[c];
-		name->ndata[i] ^= flip;
-
-		bits >>= 1;
-	}
-#endif /* if 0 */
-
 unlock:
 	NODE_UNLOCK(&rbtdb->node_locks[rbtnode->locknum].lock,
 		    isc_rwlocktype_read);