diff --git a/xdiff/xdiffi.c b/xdiff/xdiffi.c
index cb8e412c7b..8d96074414 100644
--- a/xdiff/xdiffi.c
+++ b/xdiff/xdiffi.c
@@ -22,9 +22,9 @@
 
 #include "xinclude.h"
 
-static unsigned long get_hash(xdfile_t *xdf, long index)
+static size_t get_hash(xdfile_t *xdf, long index)
 {
-	return xdf->recs[xdf->rindex[index]].ha;
+	return xdf->recs[xdf->rindex[index]].minimal_perfect_hash;
 }
 
 #define XDL_MAX_COST_MIN 256
@@ -385,7 +385,7 @@ static xdchange_t *xdl_add_change(xdchange_t *xscr, long i1, long i2, long chg1,
 
 static int recs_match(xrecord_t *rec1, xrecord_t *rec2)
 {
-	return (rec1->ha == rec2->ha);
+	return rec1->minimal_perfect_hash == rec2->minimal_perfect_hash;
 }
 
 /*
diff --git a/xdiff/xhistogram.c b/xdiff/xhistogram.c
index 6dc450b1fe..5ae1282c27 100644
--- a/xdiff/xhistogram.c
+++ b/xdiff/xhistogram.c
@@ -90,7 +90,7 @@ struct region {
 
 static int cmp_recs(xrecord_t *r1, xrecord_t *r2)
 {
-	return r1->ha == r2->ha;
+	return r1->minimal_perfect_hash == r2->minimal_perfect_hash;
 
 }
 
@@ -98,7 +98,7 @@ static int cmp_recs(xrecord_t *r1, xrecord_t *r2)
 	(cmp_recs(REC(i->env, s1, l1), REC(i->env, s2, l2)))
 
 #define TABLE_HASH(index, side, line) \
-	XDL_HASHLONG((REC(index->env, side, line))->ha, index->table_bits)
+	XDL_HASHLONG((REC(index->env, side, line))->minimal_perfect_hash, index->table_bits)
 
 static int scanA(struct histindex *index, int line1, int count1)
 {
diff --git a/xdiff/xpatience.c b/xdiff/xpatience.c
index bb61354f22..cc53266f3b 100644
--- a/xdiff/xpatience.c
+++ b/xdiff/xpatience.c
@@ -48,7 +48,7 @@
 struct hashmap {
 	int nr, alloc;
 	struct entry {
-		unsigned long hash;
+		size_t minimal_perfect_hash;
 		/*
 		 * 0 = unused entry, 1 = first line, 2 = second, etc.
 		 * line2 is NON_UNIQUE if the line is not unique
@@ -101,10 +101,10 @@ static void insert_record(xpparam_t const *xpp, int line, struct hashmap *map,
 	 * So we multiply ha by 2 in the hope that the hashing was
 	 * "unique enough".
 	 */
-	int index = (int)((record->ha << 1) % map->alloc);
+	int index = (int)((record->minimal_perfect_hash << 1) % map->alloc);
 
 	while (map->entries[index].line1) {
-		if (map->entries[index].hash != record->ha) {
+		if (map->entries[index].minimal_perfect_hash != record->minimal_perfect_hash) {
 			if (++index >= map->alloc)
 				index = 0;
 			continue;
@@ -120,7 +120,7 @@ static void insert_record(xpparam_t const *xpp, int line, struct hashmap *map,
 	if (pass == 2)
 		return;
 	map->entries[index].line1 = line;
-	map->entries[index].hash = record->ha;
+	map->entries[index].minimal_perfect_hash = record->minimal_perfect_hash;
 	map->entries[index].anchor = is_anchor(xpp, (const char *)map->env->xdf1.recs[line - 1].ptr);
 	if (!map->first)
 		map->first = map->entries + index;
@@ -248,7 +248,7 @@ static int match(struct hashmap *map, int line1, int line2)
 {
 	xrecord_t *record1 = &map->env->xdf1.recs[line1 - 1];
 	xrecord_t *record2 = &map->env->xdf2.recs[line2 - 1];
-	return record1->ha == record2->ha;
+	return record1->minimal_perfect_hash == record2->minimal_perfect_hash;
 }
 
 static int patience_diff(xpparam_t const *xpp, xdfenv_t *env,
diff --git a/xdiff/xprepare.c b/xdiff/xprepare.c
index 85e56021da..bea0992b5e 100644
--- a/xdiff/xprepare.c
+++ b/xdiff/xprepare.c
@@ -93,12 +93,12 @@ static void xdl_free_classifier(xdlclassifier_t *cf) {
 
 
 static int xdl_classify_record(unsigned int pass, xdlclassifier_t *cf, xrecord_t *rec) {
-	long hi;
+	size_t hi;
 	xdlclass_t *rcrec;
 
-	hi = (long) XDL_HASHLONG(rec->ha, cf->hbits);
+	hi = XDL_HASHLONG(rec->line_hash, cf->hbits);
 	for (rcrec = cf->rchash[hi]; rcrec; rcrec = rcrec->next)
-		if (rcrec->rec.ha == rec->ha &&
+		if (rcrec->rec.line_hash == rec->line_hash &&
 				xdl_recmatch((const char *)rcrec->rec.ptr, (long)rcrec->rec.size,
 					(const char *)rec->ptr, (long)rec->size, cf->flags))
 			break;
@@ -120,7 +120,7 @@ static int xdl_classify_record(unsigned int pass, xdlclassifier_t *cf, xrecord_t
 
 	(pass == 1) ? rcrec->len1++ : rcrec->len2++;
 
-	rec->ha = (unsigned long) rcrec->idx;
+	rec->minimal_perfect_hash = (size_t)rcrec->idx;
 
 	return 0;
 }
@@ -158,7 +158,7 @@ static int xdl_prepare_ctx(unsigned int pass, mmfile_t *mf, long narec, xpparam_
 			crec = &xdf->recs[xdf->nrec++];
 			crec->ptr = prev;
 			crec->size = cur - prev;
-			crec->ha = hav;
+			crec->line_hash = hav;
 			if (xdl_classify_record(pass, cf, crec) < 0)
 				goto abort;
 		}
@@ -290,7 +290,7 @@ static int xdl_cleanup_records(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xd
 	if ((mlim = xdl_bogosqrt(xdf1->nrec)) > XDL_MAX_EQLIMIT)
 		mlim = XDL_MAX_EQLIMIT;
 	for (i = xdf1->dstart, recs = &xdf1->recs[xdf1->dstart]; i <= xdf1->dend; i++, recs++) {
-		rcrec = cf->rcrecs[recs->ha];
+		rcrec = cf->rcrecs[recs->minimal_perfect_hash];
 		nm = rcrec ? rcrec->len2 : 0;
 		action1[i] = (nm == 0) ? DISCARD: (nm >= mlim && !need_min) ? INVESTIGATE: KEEP;
 	}
@@ -298,7 +298,7 @@ static int xdl_cleanup_records(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xd
 	if ((mlim = xdl_bogosqrt(xdf2->nrec)) > XDL_MAX_EQLIMIT)
 		mlim = XDL_MAX_EQLIMIT;
 	for (i = xdf2->dstart, recs = &xdf2->recs[xdf2->dstart]; i <= xdf2->dend; i++, recs++) {
-		rcrec = cf->rcrecs[recs->ha];
+		rcrec = cf->rcrecs[recs->minimal_perfect_hash];
 		nm = rcrec ? rcrec->len1 : 0;
 		action2[i] = (nm == 0) ? DISCARD: (nm >= mlim && !need_min) ? INVESTIGATE: KEEP;
 	}
@@ -350,7 +350,7 @@ static int xdl_trim_ends(xdfile_t *xdf1, xdfile_t *xdf2) {
 	recs2 = xdf2->recs;
 	for (i = 0, lim = XDL_MIN(xdf1->nrec, xdf2->nrec); i < lim;
 	     i++, recs1++, recs2++)
-		if (recs1->ha != recs2->ha)
+		if (recs1->minimal_perfect_hash != recs2->minimal_perfect_hash)
 			break;
 
 	xdf1->dstart = xdf2->dstart = i;
@@ -358,7 +358,7 @@ static int xdl_trim_ends(xdfile_t *xdf1, xdfile_t *xdf2) {
 	recs1 = xdf1->recs + xdf1->nrec - 1;
 	recs2 = xdf2->recs + xdf2->nrec - 1;
 	for (lim -= i, i = 0; i < lim; i++, recs1--, recs2--)
-		if (recs1->ha != recs2->ha)
+		if (recs1->minimal_perfect_hash != recs2->minimal_perfect_hash)
 			break;
 
 	xdf1->dend = xdf1->nrec - i - 1;
diff --git a/xdiff/xtypes.h b/xdiff/xtypes.h
index 354349b523..d4e9cd2e76 100644
--- a/xdiff/xtypes.h
+++ b/xdiff/xtypes.h
@@ -41,7 +41,8 @@ typedef struct s_chastore {
 typedef struct s_xrecord {
 	uint8_t const *ptr;
 	size_t size;
-	unsigned long ha;
+	uint64_t line_hash;
+	size_t minimal_perfect_hash;
 } xrecord_t;
 
 typedef struct s_xdfile {