diff --git a/jets/d/in_uni.c b/jets/d/in_uni.c
index f8b49ff099..85f07b8350 100644
--- a/jets/d/in_uni.c
+++ b/jets/d/in_uni.c
@@ -3,6 +3,68 @@
 */
 #include "all.h"
 
+/* internal functions
+*/
+
+static u3_noun
+_in_uni(u3_noun a, u3_noun b)
+{
+  u3_noun n_a, l_a, r_a,
+          n_b, l_b, r_b,
+          neb, sub, naw, pro;
+  if ( u3_nul == a ) {
+    return u3k(b);
+  }
+  else if ( u3_nul == b ) {
+    return u3k(a);
+  }
+  else if ( (c3n == u3r_trel(a, &n_a, &l_a, &r_a))
+         || (c3n == u3r_trel(b, &n_b, &l_b, &r_b)) )
+  {
+    return u3m_bail(c3__exit);
+  }
+  else if ( c3n == u3qc_vor(n_a, n_b) ) {
+    if ( c3y == u3r_sing(n_a, n_b) ) {
+      return u3nt(u3k(n_b), _in_uni(l_a, l_b), _in_uni(r_a, r_b));
+    }
+    else if ( c3y == u3qc_hor(n_a, n_b) ) {
+      naw = u3nt(u3k(n_a), u3k(l_a), u3_nul);
+      sub = _in_uni(naw, l_b);
+      neb = u3nt(u3k(n_b), sub, u3k(r_b));
+      pro = _in_uni(r_a, neb);
+      u3z(naw); u3z(neb);
+      return pro;
+    }
+    else {
+      naw = u3nt(u3k(n_a), u3_nul, u3k(r_a));
+      sub = _in_uni(naw, r_b);
+      neb = u3nt(u3k(n_b), u3k(l_b),  sub);
+      pro = _in_uni(l_a, neb);
+      u3z(naw); u3z(neb);
+      return pro;
+    }
+  }
+  else if ( c3y == u3r_sing(n_b, n_a) ) {
+    return u3nt(u3k(n_b), _in_uni(l_a, l_b), _in_uni(r_a, r_b));
+  }
+  else if ( c3y == u3qc_hor(n_b, n_a) ) {
+    neb = u3nt(u3k(n_b), u3k(l_b), u3_nul);
+    sub = _in_uni(l_a, neb);
+    naw = u3nt(u3k(n_a), sub, u3k(r_a));
+    pro = _in_uni(naw, r_b);
+    u3z(neb); u3z(naw);
+    return pro;
+  }
+  else {
+    neb = u3nt(u3k(n_b), u3_nul, u3k(r_b));
+    sub = _in_uni(r_a, neb);
+    naw = u3nt(u3k(n_a), u3k(l_a), sub);
+    pro = _in_uni(naw, l_b);
+    u3z(neb); u3z(naw);
+    return pro;
+  }
+}
+
 
 /* functions
 */
@@ -21,86 +83,11 @@
   u3qdi_uni(u3_noun a,
             u3_noun b)
   {
-    if ( u3_nul == a ) {
-      return u3k(b);
-    }
-    else if ( u3_nul == b ) {
+    if ( c3y == u3r_sing(a, b) ) {
       return u3k(a);
     }
     else {
-      u3_noun l_a, n_a, r_a, lr_a;
-      u3_noun l_b, n_b, r_b, lr_b;
-
-      if ( (c3n == u3r_cell(a, &n_a, &lr_a)) ) {
-        return u3m_bail(c3__exit);
-      }
-      else if ( (c3n == u3r_cell(b, &n_b, &lr_b)) ) {
-        return u3m_bail(c3__exit);
-      }
-      else {
-        if ( c3y == u3qc_vor(n_a, n_b) ) {
-          if ( c3n == u3r_cell(lr_a, &l_a, &r_a) ) {
-            return u3m_bail(c3__exit);
-          }
-          else if ( c3n == u3r_cell(lr_b, &l_b, &r_b) ) {
-            return u3m_bail(c3__exit);
-          }
-          else if ( c3y == u3r_sing(n_a, n_b) ) {
-            return u3nt(u3k(n_b),
-                        u3kdi_uni(u3k(l_a), u3k(l_b)),
-                        u3kdi_uni(u3k(r_a), u3k(r_b)));
-          }
-          else if ( c3y == u3qc_hor(n_b, n_a) ) {
-            return u3kdi_uni(u3nt(u3k(n_a),
-                                  u3kdi_uni(u3k(l_a),
-                                            u3nt(u3k(n_b),
-                                                 u3k(l_b),
-                                                 u3_nul)),
-                                  u3k(r_a)),
-                             u3k(r_b));
-          }
-          else {
-            return u3kdi_uni(u3nt(u3k(n_a),
-                                  u3k(l_a),
-                                  u3kdi_uni(u3k(r_a),
-                                            u3nt(u3k(n_b),
-                                                 u3_nul,
-                                                 u3k(r_b)))),
-                             u3k(l_b));
-          }
-        }
-        else {
-          if ( c3n == u3r_cell(lr_b, &l_b, &r_b) ) {
-            return u3m_bail(c3__exit);
-          }
-          else if ( c3n == u3r_cell(lr_a, &l_a, &r_a) ) {
-            return u3m_bail(c3__exit);
-          }
-          else if ( c3y == u3r_sing(n_b, n_a) ) {
-            return u3nt(u3k(n_b),
-                        u3kdi_uni(u3k(l_a), u3k(l_b)),
-                        u3kdi_uni(u3k(r_a), u3k(r_b)));
-          }
-          else if ( c3y == u3qc_hor(n_a, n_b) ) {
-            return u3kdi_uni(u3k(r_a),
-                             u3nt(u3k(n_b),
-                                  u3kdi_uni(u3nt(u3k(n_a),
-                                                 u3k(l_a),
-                                                 u3_nul),
-                                            u3k(l_b)),
-                                  u3k(r_b)));
-          }
-          else {
-            return u3kdi_uni(u3k(l_a),
-                             u3nt(u3k(n_b),
-                                  u3k(l_b),
-                                  u3kdi_uni(u3nt(u3k(n_a),
-                                                 u3_nul,
-                                                 u3k(r_a)),
-                                            u3k(r_b))));
-          }
-        }
-      }
+      return _in_uni(a, b);
     }
   }
   u3_noun
diff --git a/jets/tree.c b/jets/tree.c
index 1dff8ffebc..497c8b06f6 100644
--- a/jets/tree.c
+++ b/jets/tree.c
@@ -424,7 +424,7 @@ static u3j_core _149_tri_d[] =
     // static u3j_harm _149_two__in_int_a[] = {{".2", u3wdi_int}, {}};
     static u3j_harm _149_two__in_put_a[] = {{".2", u3wdi_put}, {}};
     static u3j_harm _149_two__in_tap_a[] = {{".2", u3wdi_tap}, {}};
-    // static u3j_harm _149_two__in_uni_a[] = {{".2", u3wdi_uni}, {}};
+    static u3j_harm _149_two__in_uni_a[] = {{".2", u3wdi_uni}, {}};
   static u3j_core _149_two__in_d[] =
     { { "bif", _149_two__in_bif_a },
       { "dif", _149_two__in_dif_a },
@@ -434,7 +434,7 @@ static u3j_core _149_tri_d[] =
       // { "int", _149_two__in_int_a },
       { "put", _149_two__in_put_a },
       { "tap", _149_two__in_tap_a },
-      // { "uni", _149_two__in_uni_a },
+      { "uni", _149_two__in_uni_a },
       {}
     };
 
@@ -988,7 +988,7 @@ static u3j_core _150_tri_d[] =
     // static u3j_harm _150_two__in_int_a[] = {{".2", u3wdi_int}, {}};
     static u3j_harm _150_two__in_put_a[] = {{".2", u3wdi_put}, {}};
     static u3j_harm _150_two__in_tap_a[] = {{".2", u3wdi_tap}, {}};
-    // static u3j_harm _150_two__in_uni_a[] = {{".2", u3wdi_uni}, {}};
+    static u3j_harm _150_two__in_uni_a[] = {{".2", u3wdi_uni}, {}};
   static u3j_core _150_two__in_d[] =
     { { "bif", _150_two__in_bif_a },
       { "dif", _150_two__in_dif_a },
@@ -998,7 +998,7 @@ static u3j_core _150_tri_d[] =
       // { "int", _150_two__in_int_a },
       { "put", _150_two__in_put_a },
       { "tap", _150_two__in_tap_a },
-      // { "uni", _150_two__in_uni_a },
+      { "uni", _150_two__in_uni_a },
       {}
     };