diff --git a/include/jemalloc/internal/emap.h b/include/jemalloc/internal/emap.h
index fcc9fe4c..7835da96 100644
--- a/include/jemalloc/internal/emap.h
+++ b/include/jemalloc/internal/emap.h
@@ -86,5 +86,9 @@ void emap_split_commit(tsdn_t *tsdn, emap_t *emap,
     emap_split_prepare_t *split_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);
+void emap_merge_prepare(tsdn_t *tsdn, emap_t *emap, rtree_ctx_t *rtree_ctx,
+    emap_split_prepare_t *split_prepare, edata_t *lead, edata_t *trail);
+void emap_merge_commit(tsdn_t *tsdn, emap_t *emap,
+    emap_split_prepare_t *split_prepare, edata_t *lead, edata_t *trail);
 
 #endif /* JEMALLOC_INTERNAL_EMAP_H */
diff --git a/src/emap.c b/src/emap.c
index b79b66af..bde986f0 100644
--- a/src/emap.c
+++ b/src/emap.c
@@ -236,3 +236,40 @@ emap_split_commit(tsdn_t *tsdn, emap_t *emap,
 	emap_rtree_write_acquired(tsdn, emap, split_prepare->trail_elm_a,
 	    split_prepare->trail_elm_b, trail, szind_b, slab_b);
 }
+
+void
+emap_merge_prepare(tsdn_t *tsdn, emap_t *emap, rtree_ctx_t *rtree_ctx,
+    emap_split_prepare_t *split_prepare, edata_t *lead, edata_t *trail) {
+	emap_rtree_leaf_elms_lookup(tsdn, emap, rtree_ctx, lead, true, false,
+	    &split_prepare->lead_elm_a, &split_prepare->lead_elm_b);
+	emap_rtree_leaf_elms_lookup(tsdn, emap, rtree_ctx, trail, true, false,
+	    &split_prepare->trail_elm_a, &split_prepare->trail_elm_b);
+}
+
+void
+emap_merge_commit(tsdn_t *tsdn, emap_t *emap,
+    emap_split_prepare_t *split_prepare, edata_t *lead, edata_t *trail) {
+	if (split_prepare->lead_elm_b != NULL) {
+		rtree_leaf_elm_write(tsdn, &emap->rtree,
+		    split_prepare->lead_elm_b, NULL, SC_NSIZES, false);
+	}
+
+	rtree_leaf_elm_t *merged_b;
+	if (split_prepare->trail_elm_b != NULL) {
+		rtree_leaf_elm_write(tsdn, &emap->rtree,
+		    split_prepare->trail_elm_a, NULL, SC_NSIZES, false);
+		merged_b = split_prepare->trail_elm_b;
+	} else {
+		merged_b = split_prepare->trail_elm_a;
+	}
+
+	edata_size_set(lead, edata_size_get(lead) + edata_size_get(trail));
+	edata_szind_set(lead, SC_NSIZES);
+	edata_sn_set(lead, (edata_sn_get(lead) < edata_sn_get(trail)) ?
+	    edata_sn_get(lead) : edata_sn_get(trail));
+	edata_zeroed_set(lead, edata_zeroed_get(lead)
+	    && edata_zeroed_get(trail));
+
+	emap_rtree_write_acquired(tsdn, emap, split_prepare->lead_elm_a,
+	    merged_b, lead, SC_NSIZES, false);
+}
diff --git a/src/extent.c b/src/extent.c
index e8a12574..3db82a70 100644
--- a/src/extent.c
+++ b/src/extent.c
@@ -1342,33 +1342,11 @@ extent_merge_impl(tsdn_t *tsdn, ehooks_t *ehooks, edata_cache_t *edata_cache,
 	 */
 	rtree_ctx_t rtree_ctx_fallback;
 	rtree_ctx_t *rtree_ctx = tsdn_rtree_ctx(tsdn, &rtree_ctx_fallback);
-	rtree_leaf_elm_t *a_elm_a, *a_elm_b, *b_elm_a, *b_elm_b;
-	emap_rtree_leaf_elms_lookup(tsdn, &emap_global, rtree_ctx, a, true,
-	    false, &a_elm_a, &a_elm_b);
-	emap_rtree_leaf_elms_lookup(tsdn, &emap_global, rtree_ctx, b, true,
-	    false, &b_elm_a, &b_elm_b);
-
+	emap_split_prepare_t split_prepare;
+	emap_merge_prepare(tsdn, &emap_global, rtree_ctx, &split_prepare, a, b);
 	emap_lock_edata2(tsdn, &emap_global, a, b);
 
-	if (a_elm_b != NULL) {
-		rtree_leaf_elm_write(tsdn, &emap_global.rtree, a_elm_b, NULL,
-		    SC_NSIZES, false);
-	}
-	if (b_elm_b != NULL) {
-		rtree_leaf_elm_write(tsdn, &emap_global.rtree, b_elm_a, NULL,
-		    SC_NSIZES, false);
-	} else {
-		b_elm_b = b_elm_a;
-	}
-
-	edata_size_set(a, edata_size_get(a) + edata_size_get(b));
-	edata_szind_set(a, SC_NSIZES);
-	edata_sn_set(a, (edata_sn_get(a) < edata_sn_get(b)) ?
-	    edata_sn_get(a) : edata_sn_get(b));
-	edata_zeroed_set(a, edata_zeroed_get(a) && edata_zeroed_get(b));
-
-	emap_rtree_write_acquired(tsdn, &emap_global, a_elm_a, b_elm_b, a,
-	    SC_NSIZES, false);
+	emap_merge_commit(tsdn, &emap_global, &split_prepare, a, b);
 
 	emap_unlock_edata2(tsdn, &emap_global, a, b);