diff --git a/include/jemalloc/internal/ql.h b/include/jemalloc/internal/ql.h
index 80290407..93ddce58 100644
--- a/include/jemalloc/internal/ql.h
+++ b/include/jemalloc/internal/ql.h
@@ -58,6 +58,16 @@ struct {								\
 	ql_first(a_head) = qr_next((a_elm), a_field);			\
 } while (0)
 
+#define ql_concat(a_head_a, a_head_b, a_field) do {			\
+	if (ql_first(a_head_a) == NULL) {				\
+		ql_first(a_head_a) = ql_first(a_head_b);		\
+	} else if (ql_first(a_head_b) != NULL) {			\
+		qr_meld(ql_first(a_head_a), ql_first(a_head_b),		\
+		    a_field);						\
+	}								\
+	ql_first(a_head_b) = NULL;					\
+} while (0)
+
 #define ql_remove(a_head, a_elm, a_field) do {				\
 	if (ql_first(a_head) == (a_elm)) {				\
 		ql_first(a_head) = qr_next(ql_first(a_head), a_field);	\
@@ -79,6 +89,15 @@ struct {								\
 	ql_remove((a_head), t, a_field);				\
 } while (0)
 
+#define ql_split(a_head_a, a_elm, a_head_b, a_field) do {		\
+	if (ql_first(a_head_a) == (a_elm)) {				\
+		ql_first(a_head_a) = NULL;				\
+	} else {							\
+		qr_split(ql_first(a_head_a), (a_elm), a_field);		\
+	}								\
+	ql_first(a_head_b) = (a_elm);					\
+} while (0)
+
 #define ql_foreach(a_var, a_head, a_field)				\
 	qr_foreach((a_var), ql_first(a_head), a_field)
 
diff --git a/test/unit/ql.c b/test/unit/ql.c
index 04da35fe..c2b19812 100644
--- a/test/unit/ql.c
+++ b/test/unit/ql.c
@@ -192,6 +192,72 @@ TEST_BEGIN(test_ql_insert) {
 }
 TEST_END
 
+static void
+test_concat_split_entries(list_t *entries, unsigned nentries_a,
+    unsigned nentries_b) {
+	init_entries(entries, nentries_a + nentries_b);
+
+	list_head_t head_a;
+	ql_new(&head_a);
+	for (unsigned i = 0; i < nentries_a; i++) {
+		ql_tail_insert(&head_a, &entries[i], link);
+	}
+	if (nentries_a == 0) {
+		test_empty_list(&head_a);
+	} else {
+		test_entries_list(&head_a, entries, nentries_a);
+	}
+
+	list_head_t head_b;
+	ql_new(&head_b);
+	for (unsigned i = 0; i < nentries_b; i++) {
+		ql_tail_insert(&head_b, &entries[nentries_a + i], link);
+	}
+	if (nentries_b == 0) {
+		test_empty_list(&head_b);
+	} else {
+		test_entries_list(&head_b, entries + nentries_a, nentries_b);
+	}
+
+	ql_concat(&head_a, &head_b, link);
+	if (nentries_a + nentries_b == 0) {
+		test_empty_list(&head_a);
+	} else {
+		test_entries_list(&head_a, entries, nentries_a + nentries_b);
+	}
+	test_empty_list(&head_b);
+
+	if (nentries_b == 0) {
+		return;
+	}
+
+	list_head_t head_c;
+	ql_split(&head_a, &entries[nentries_a], &head_c, link);
+	if (nentries_a == 0) {
+		test_empty_list(&head_a);
+	} else {
+		test_entries_list(&head_a, entries, nentries_a);
+	}
+	test_entries_list(&head_c, entries + nentries_a, nentries_b);
+}
+
+TEST_BEGIN(test_ql_concat_split) {
+	list_t entries[NENTRIES];
+
+	test_concat_split_entries(entries, 0, 0);
+
+	test_concat_split_entries(entries, 0, 1);
+	test_concat_split_entries(entries, 1, 0);
+
+	test_concat_split_entries(entries, 0, NENTRIES);
+	test_concat_split_entries(entries, 1, NENTRIES - 1);
+	test_concat_split_entries(entries, NENTRIES / 2,
+	    NENTRIES - NENTRIES / 2);
+	test_concat_split_entries(entries, NENTRIES - 1, 1);
+	test_concat_split_entries(entries, NENTRIES, 0);
+}
+TEST_END
+
 int
 main(void) {
 	return test(
@@ -200,5 +266,6 @@ main(void) {
 	    test_ql_tail_remove,
 	    test_ql_head_insert,
 	    test_ql_head_remove,
-	    test_ql_insert);
+	    test_ql_insert,
+	    test_ql_concat_split);
 }