diff --git a/include/jemalloc/internal/emap.h b/include/jemalloc/internal/emap.h
index 5fc713d3..b7eed84d 100644
--- a/include/jemalloc/internal/emap.h
+++ b/include/jemalloc/internal/emap.h
@@ -110,11 +110,9 @@ struct emap_prepare_s {
  * state appropriately.
  */
 bool emap_split_prepare(tsdn_t *tsdn, emap_t *emap, emap_prepare_t *prepare,
-    edata_t *edata, size_t size_a, szind_t szind_a, bool slab_a, edata_t *trail,
-    size_t size_b, szind_t szind_b, bool slab_b);
+    edata_t *edata, size_t size_a, edata_t *trail, size_t size_b);
 void emap_split_commit(tsdn_t *tsdn, emap_t *emap, emap_prepare_t *prepare,
-    edata_t *lead, size_t size_a, szind_t szind_a, bool slab_a, edata_t *trail,
-    size_t size_b, szind_t szind_b, bool slab_b);
+    edata_t *lead, size_t size_a, edata_t *trail, size_t size_b);
 void emap_merge_prepare(tsdn_t *tsdn, emap_t *emap, emap_prepare_t *prepare,
     edata_t *lead, edata_t *trail);
 void emap_merge_commit(tsdn_t *tsdn, emap_t *emap, emap_prepare_t *prepare,
diff --git a/src/emap.c b/src/emap.c
index 0d10c79e..f7fac013 100644
--- a/src/emap.c
+++ b/src/emap.c
@@ -230,8 +230,7 @@ void emap_remap(tsdn_t *tsdn, emap_t *emap, edata_t *edata, szind_t szind,
 
 bool
 emap_split_prepare(tsdn_t *tsdn, emap_t *emap, emap_prepare_t *prepare,
-    edata_t *edata, size_t size_a, szind_t szind_a, bool slab_a, edata_t *trail,
-    size_t size_b, szind_t szind_b, bool slab_b) {
+    edata_t *edata, size_t size_a, edata_t *trail, size_t size_b) {
 	EMAP_DECLARE_RTREE_CTX;
 
 	/*
@@ -240,7 +239,7 @@ emap_split_prepare(tsdn_t *tsdn, emap_t *emap, emap_prepare_t *prepare,
 	 * facilitate a lookup.
 	 */
 	edata_t lead;
-	edata_init(&lead, 0U, edata_addr_get(edata), size_a, slab_a, szind_a, 0,
+	edata_init(&lead, 0U, edata_addr_get(edata), size_a, false, 0, 0,
 	    extent_state_active, false, false, false, EXTENT_NOT_HEAD);
 
 	emap_rtree_leaf_elms_lookup(tsdn, emap, rtree_ctx, &lead, false, true,
@@ -257,12 +256,19 @@ emap_split_prepare(tsdn_t *tsdn, emap_t *emap, emap_prepare_t *prepare,
 
 void
 emap_split_commit(tsdn_t *tsdn, emap_t *emap, emap_prepare_t *prepare,
-    edata_t *lead, size_t size_a, szind_t szind_a, bool slab_a, edata_t *trail,
-    size_t size_b, szind_t szind_b, bool slab_b) {
+    edata_t *lead, size_t size_a, edata_t *trail, size_t size_b) {
+	/*
+	 * We should think about not writing to the lead leaf element.  We can
+	 * get into situations where a racing realloc-like call can disagree
+	 * with a size lookup request.  I think it's fine to declare that these
+	 * situations are race bugs, but there's an argument to be made that for
+	 * things like xallocx, a size lookup call should return either the old
+	 * size or the new size, but not anything else.
+	 */
 	emap_rtree_write_acquired(tsdn, emap, prepare->lead_elm_a,
-	    prepare->lead_elm_b, lead, szind_a, slab_a);
+	    prepare->lead_elm_b, lead, SC_NSIZES, /* slab */ false);
 	emap_rtree_write_acquired(tsdn, emap, prepare->trail_elm_a,
-	    prepare->trail_elm_b, trail, szind_b, slab_b);
+	    prepare->trail_elm_b, trail, SC_NSIZES, /* slab */ false);
 }
 
 void
diff --git a/src/extent.c b/src/extent.c
index 671699ca..073f8065 100644
--- a/src/extent.c
+++ b/src/extent.c
@@ -1190,8 +1190,7 @@ extent_split_impl(tsdn_t *tsdn, pa_shard_t *shard, ehooks_t *ehooks,
 	    EXTENT_NOT_HEAD);
 	emap_prepare_t prepare;
 	bool err = emap_split_prepare(tsdn, shard->emap, &prepare, edata,
-	    size_a, SC_NSIZES, /* slab */ false, trail, size_b, SC_NSIZES,
-	    /* slab */ false);
+	    size_a, trail, size_b);
 	if (err) {
 		goto label_error_b;
 	}
@@ -1206,8 +1205,8 @@ extent_split_impl(tsdn_t *tsdn, pa_shard_t *shard, ehooks_t *ehooks,
 	}
 
 	edata_size_set(edata, size_a);
-	emap_split_commit(tsdn, shard->emap, &prepare, edata, size_a, SC_NSIZES,
-	    /* slab_a */ false, trail, size_b,SC_NSIZES, /* slab_b */ false);
+	emap_split_commit(tsdn, shard->emap, &prepare, edata, size_a, trail,
+	    size_b);
 
 	emap_unlock_edata2(tsdn, shard->emap, edata, trail);