diff --git a/C/arith1.c b/C/arith1.c
index f495bb632..683f6b620 100644
--- a/C/arith1.c
+++ b/C/arith1.c
@@ -240,7 +240,7 @@ eval1(Int fi, Term t) {
 	RBIG(&new);
       }
 #endif
-    case db_ref_e:
+    default:
       RERROR();
     }
   case op_unot:
@@ -259,7 +259,7 @@ eval1(Int fi, Term t) {
 	RBIG(&new);
       }
 #endif
-    case db_ref_e:
+    default:
       RERROR();
     }
   case op_exp:
@@ -480,7 +480,7 @@ eval1(Int fi, Term t) {
 	}
 	break;
 #endif
-      case db_ref_e:
+      default:
 	RERROR();
       }
 #if HAVE_ISNAN
@@ -518,7 +518,7 @@ eval1(Int fi, Term t) {
 	}
 	break;
 #endif
-      case db_ref_e:
+      default:
 	RERROR();
       }
 #if HAVE_ISNAN
@@ -555,7 +555,7 @@ eval1(Int fi, Term t) {
 	}
 	return t;
 	break;
-      case db_ref_e:
+      default:
 #endif
 	RERROR();
       }
@@ -591,7 +591,7 @@ eval1(Int fi, Term t) {
 	  return Yap_ArithError(TYPE_ERROR_FLOAT, t, "X is round(BIGNUM)");
 	}
 	return t;
-      case db_ref_e:
+      default:
 #endif
 	RERROR();
       }
@@ -629,7 +629,7 @@ eval1(Int fi, Term t) {
 #ifdef USE_GMP
       RFLOAT(mpz_get_d(Yap_BigIntOfTerm(t)));
 #endif
-    case db_ref_e:
+    default:
       RERROR();
     }
   case op_abs:
@@ -648,7 +648,7 @@ eval1(Int fi, Term t) {
 	RBIG(&new);
       }
 #endif
-    case db_ref_e:
+    default:
       RERROR();
     }
   case op_msb:
@@ -667,7 +667,7 @@ eval1(Int fi, Term t) {
 	RINT(mpz_sizeinbase(big,2));
       }
 #endif
-    case db_ref_e:
+    default:
       RERROR();
     }
   case op_lsb:
@@ -686,7 +686,7 @@ eval1(Int fi, Term t) {
 	RINT(mpz_scan1(big,0));
       }
 #endif
-    case db_ref_e:
+    default:
       RERROR();
     }
   case op_popcount:
@@ -705,7 +705,7 @@ eval1(Int fi, Term t) {
 	RINT(mpz_popcount(big));
       }
 #endif
-    case db_ref_e:
+    default:
       RERROR();
     }
   case op_ffracp:
@@ -731,7 +731,7 @@ eval1(Int fi, Term t) {
 	RFLOAT(0.0);
       }
 #endif
-    case db_ref_e:
+    default:
       RERROR();
     }
   case op_fintp:
@@ -753,7 +753,7 @@ eval1(Int fi, Term t) {
 	RFLOAT(mpz_get_d(Yap_BigIntOfTerm(t)));
       }
 #endif
-    case db_ref_e:
+    default:
       RERROR();
     }
   case op_sign:
@@ -775,7 +775,7 @@ eval1(Int fi, Term t) {
 #ifdef USE_GMP
       RINT(mpz_sgn(Yap_BigIntOfTerm(t)));
 #endif
-    case db_ref_e:
+    default:
       RERROR();
     }
   case op_random1:
@@ -788,7 +788,7 @@ eval1(Int fi, Term t) {
 #ifdef USE_GMP
       return Yap_ArithError(TYPE_ERROR_INTEGER, t, "random(%f)", FloatOfTerm(t));
 #endif
-    case db_ref_e:
+    default:
       RERROR();
     }
   }
diff --git a/C/arith2.c b/C/arith2.c
index 250cb5ed6..c3bb0f80c 100644
--- a/C/arith2.c
+++ b/C/arith2.c
@@ -93,7 +93,7 @@ p_mod(Term t1, Term t2) {
 #ifdef USE_GMP
       return Yap_gmp_mod_int_big(IntegerOfTerm(t1), Yap_BigIntOfTerm(t2));
 #endif
-    case db_ref_e:
+    default:
       RERROR();
       break;
     }
@@ -115,11 +115,11 @@ p_mod(Term t1, Term t2) {
       return Yap_gmp_mod_big_big(Yap_BigIntOfTerm(t1), Yap_BigIntOfTerm(t2));
     case double_e:
       return Yap_ArithError(TYPE_ERROR_INTEGER, t2, "mod/2");
-    case db_ref_e:
+    default:
       RERROR();
     }
 #endif
-  case db_ref_e:
+  default:
     RERROR();
   }
 zero_divisor:
@@ -157,7 +157,7 @@ p_rem(Term t1, Term t2) {
       /* I know the term is much larger, so: */
       RINT(IntegerOfTerm(t1));
 #endif
-    case db_ref_e:
+    default:
       RERROR();
     }
     break;
@@ -191,11 +191,11 @@ p_rem(Term t1, Term t2) {
       }
     case double_e:
       return Yap_ArithError(TYPE_ERROR_INTEGER, t2, "mod/2");
-    case db_ref_e:
+    default:
       RERROR();
     }
 #endif
-  case db_ref_e:
+  default:
     RERROR();
   }
  zero_divisor:
@@ -234,7 +234,7 @@ p_fdiv(Term t1, Term t2)
 	RFLOAT(((Float)i1/f2));
       }
 #endif
-    case db_ref_e:
+    default:
       RERROR();
     }
     break;
@@ -257,7 +257,7 @@ p_fdiv(Term t1, Term t2)
 	RFLOAT(FloatOfTerm(t1)/mpz_get_d(Yap_BigIntOfTerm(t2)));
       }
 #endif
-    case db_ref_e:
+    default:
       RERROR();
     }
     break;
@@ -278,11 +278,11 @@ p_fdiv(Term t1, Term t2)
 	Float dbl = FloatOfTerm(t2);
 	RFLOAT(mpz_get_d(Yap_BigIntOfTerm(t1))/dbl);
       }
-    case db_ref_e:
+    default:
       RERROR();
     }
 #endif
-  case db_ref_e:
+  default:
     RERROR();
   }
   RERROR();
@@ -334,7 +334,7 @@ p_xor(Term t1, Term t2)
 	RBIG(&new);
       }
 #endif
-    case db_ref_e:
+    default:
       RERROR();
     }
     break;
@@ -362,11 +362,11 @@ p_xor(Term t1, Term t2)
       }
     case double_e:
       return Yap_ArithError(TYPE_ERROR_INTEGER, t2, "#/2");
-    case db_ref_e:
+    default:
       RERROR();
     }
 #endif
-  case db_ref_e:
+  default:
     RERROR();
   }
   RERROR();
@@ -394,7 +394,7 @@ p_atan2(Term t1, Term t2)
 	RFLOAT(atan2(i1,f2));
       }
 #endif
-    case db_ref_e:
+    default:
       RERROR();
       break;
     }
@@ -417,7 +417,7 @@ p_atan2(Term t1, Term t2)
 	RFLOAT(atan2(FloatOfTerm(t1),mpz_get_d(Yap_BigIntOfTerm(t2))));
       }
 #endif
-    case db_ref_e:
+    default:
       RERROR();
     }
     break;
@@ -437,11 +437,11 @@ p_atan2(Term t1, Term t2)
 	Float dbl = FloatOfTerm(t2);
 	RFLOAT(atan2(mpz_get_d(Yap_BigIntOfTerm(t1)),dbl));
       }
-    case db_ref_e:
+    default:
       RERROR();
     }
 #endif
-  case db_ref_e:
+  default:
     RERROR();
   }
   RERROR();
@@ -479,7 +479,7 @@ p_power(Term t1, Term t2)
 	RFLOAT(pow(i1,f2));
       }
 #endif
-    case db_ref_e:
+    default:
       RERROR();
     }
     break;
@@ -502,7 +502,7 @@ p_power(Term t1, Term t2)
 	RFLOAT(pow(FloatOfTerm(t1),mpz_get_d(Yap_BigIntOfTerm(t2))));
       }
 #endif
-    case db_ref_e:
+    default:
       RERROR();
     }
     break;
@@ -522,11 +522,11 @@ p_power(Term t1, Term t2)
 	Float dbl = FloatOfTerm(t2);
 	RFLOAT(pow(mpz_get_d(Yap_BigIntOfTerm(t1)),dbl));
       }
-    case db_ref_e:
+    default:
       RERROR();
     }
 #endif
-  case db_ref_e:
+  default:
     RERROR();
   }
   RERROR();
@@ -605,7 +605,7 @@ p_exp(Term t1, Term t2)
 	return Yap_ArithError(RESOURCE_ERROR_HUGE_INT, t2, "^/2");
       }
 #endif
-    case db_ref_e:
+    default:
       RERROR();
     }
     break;
@@ -628,7 +628,7 @@ p_exp(Term t1, Term t2)
 	return Yap_ArithError(RESOURCE_ERROR_HUGE_INT, t2, "^/2");
       }
 #endif
-    case db_ref_e:
+    default:
       RERROR();
     }
     break;
@@ -649,11 +649,11 @@ p_exp(Term t1, Term t2)
 	Float dbl = FloatOfTerm(t2);
 	RFLOAT(pow(mpz_get_d(Yap_BigIntOfTerm(t1)),dbl));
       }
-    case db_ref_e:
+    default:
       RERROR();
     }
 #endif
-  case db_ref_e:
+  default:
     RERROR();
   }
   RERROR();
@@ -741,7 +741,7 @@ p_gcd(Term t1, Term t2)
 	}
       }
 #endif
-    case db_ref_e:
+    default:
       RERROR();
     }
     break;
@@ -774,11 +774,11 @@ p_gcd(Term t1, Term t2)
       }
     case double_e:
       return Yap_ArithError(TYPE_ERROR_INTEGER, t2, "gcd/2");
-    case db_ref_e:
+    default:
       RERROR();
     }
 #endif
-  case db_ref_e:
+  default:
     RERROR();
   }
   RERROR();
@@ -821,7 +821,7 @@ p_min(Term t1, Term t2)
 	return t1;
       }
 #endif
-    case db_ref_e:
+    default:
       RERROR();
     }
     break;
@@ -858,7 +858,7 @@ p_min(Term t1, Term t2)
 	}
       }
 #endif
-    case db_ref_e:
+    default:
       RERROR();
     }
     break;
@@ -897,11 +897,11 @@ p_min(Term t1, Term t2)
 	  return t1;
 	}
       }
-    case db_ref_e:
+    default:
       RERROR();
     }
 #endif
-  case db_ref_e:
+  default:
     RERROR();
   }
   RERROR();
@@ -944,7 +944,7 @@ p_max(Term t1, Term t2)
 	return t1;
       }
 #endif
-    case db_ref_e:
+    default:
       RERROR();
     }
     break;
@@ -981,7 +981,7 @@ p_max(Term t1, Term t2)
 	}
       }
 #endif
-    case db_ref_e:
+    default:
       RERROR();
     }
     break;
@@ -1020,11 +1020,11 @@ p_max(Term t1, Term t2)
 	  return t1;
 	}
       }
-    case db_ref_e:
+    default:
       RERROR();
     }
 #endif
-  case db_ref_e:
+  default:
     RERROR();
   }
   RERROR();
diff --git a/H/TermExt.h b/H/TermExt.h
index 184843b00..b893ac534 100644
--- a/H/TermExt.h
+++ b/H/TermExt.h
@@ -518,6 +518,8 @@ unify_extension (Functor f, CELL d0, CELL * pt0, CELL d1)
     {
     case db_ref_e:
       return (d0 == d1);
+    case attvar_e:
+      return (d0 == d1);
     case long_int_e:
       return (pt0[1] == RepAppl (d1)[1]);
     case big_int_e:
diff --git a/H/arith2.h b/H/arith2.h
index f4988dc03..bfc6cac22 100644
--- a/H/arith2.h
+++ b/H/arith2.h
@@ -158,7 +158,7 @@ p_plus(Term t1, Term t2) {
 #ifdef USE_GMP
       return(Yap_gmp_add_int_big(IntegerOfTerm(t1), Yap_BigIntOfTerm(t2)));
 #endif
-    case db_ref_e:
+    default:
       RERROR();
     }
   case double_e:
@@ -172,7 +172,7 @@ p_plus(Term t1, Term t2) {
 #ifdef USE_GMP
       return(Yap_gmp_add_float_big(FloatOfTerm(t1),Yap_BigIntOfTerm(t2)));
 #endif
-    case db_ref_e:
+    default:
       RERROR();
     }
   case big_int_e:
@@ -185,11 +185,11 @@ p_plus(Term t1, Term t2) {
       return(Yap_gmp_add_big_big(Yap_BigIntOfTerm(t1), Yap_BigIntOfTerm(t2)));
     case double_e:
       return(Yap_gmp_add_float_big(FloatOfTerm(t2),Yap_BigIntOfTerm(t1)));
-    case db_ref_e:
+    default:
       RERROR();
     }
 #endif
-  case db_ref_e:
+  default:
     RERROR();
   }
   RERROR();
@@ -214,7 +214,7 @@ p_minus(Term t1, Term t2) {
 #ifdef USE_GMP
       return(Yap_gmp_sub_int_big(IntegerOfTerm(t1), Yap_BigIntOfTerm(t2)));
 #endif
-    case db_ref_e:
+    default:
       RERROR();
     }
     break;
@@ -231,7 +231,7 @@ p_minus(Term t1, Term t2) {
 #ifdef USE_GMP
       return(Yap_gmp_sub_float_big(FloatOfTerm(t1),Yap_BigIntOfTerm(t2)));
 #endif
-    case db_ref_e:
+    default:
       RERROR();
     }
     break;
@@ -244,11 +244,11 @@ p_minus(Term t1, Term t2) {
       return(Yap_gmp_sub_big_big(Yap_BigIntOfTerm(t1), Yap_BigIntOfTerm(t2)));
     case double_e:
       return(Yap_gmp_sub_big_float(Yap_BigIntOfTerm(t1),FloatOfTerm(t2)));
-    case db_ref_e:
+    default:
       RERROR();
     }
 #endif
-  case db_ref_e:
+  default:
     RERROR();
   }
   RERROR();
@@ -274,7 +274,7 @@ p_times(Term t1, Term t2) {
 #ifdef USE_GMP
       return(Yap_gmp_mul_int_big(IntegerOfTerm(t1), Yap_BigIntOfTerm(t2)));
 #endif
-    case db_ref_e:
+    default:
       RERROR();
     }
     break;
@@ -289,7 +289,7 @@ p_times(Term t1, Term t2) {
 #ifdef USE_GMP
       return(Yap_gmp_mul_float_big(FloatOfTerm(t1),Yap_BigIntOfTerm(t2)));
 #endif
-    case db_ref_e:
+    default:
       RERROR();
     }
     break;
@@ -303,11 +303,11 @@ p_times(Term t1, Term t2) {
       return(Yap_gmp_mul_big_big(Yap_BigIntOfTerm(t1), Yap_BigIntOfTerm(t2)));
     case double_e:
       return(Yap_gmp_mul_float_big(FloatOfTerm(t2),Yap_BigIntOfTerm(t1)));
-    case db_ref_e:
+    default:
       RERROR();
     }
 #endif
-  case db_ref_e:
+  default:
     RERROR();
   }
   RERROR();
@@ -343,7 +343,7 @@ p_div(Term t1, Term t2) {
       /* Cool */
       RINT(0);
 #endif
-    case db_ref_e:
+    default:
       RERROR();
     }
     break;
@@ -360,11 +360,11 @@ p_div(Term t1, Term t2) {
       return Yap_gmp_div_big_big(Yap_BigIntOfTerm(t1), Yap_BigIntOfTerm(t2));
     case double_e:
       return Yap_ArithError(TYPE_ERROR_INTEGER, t2, "// /2");
-    case db_ref_e:
+    default:
       RERROR();
     }
 #endif
-  case db_ref_e:
+  default:
     RERROR();
   }
   RERROR();
@@ -384,7 +384,7 @@ p_and(Term t1, Term t2) {
 #ifdef USE_GMP
       return(Yap_gmp_and_int_big(IntegerOfTerm(t1),Yap_BigIntOfTerm(t2)));
 #endif
-    case db_ref_e:
+    default:
       RERROR();
     }
     break;
@@ -401,11 +401,11 @@ p_and(Term t1, Term t2) {
       return(Yap_gmp_and_big_big(Yap_BigIntOfTerm(t2), Yap_BigIntOfTerm(t1)));
     case double_e:
       return Yap_ArithError(TYPE_ERROR_INTEGER, t2, "/\\ /2");
-    case db_ref_e:
+    default:
       RERROR();
     }
 #endif
-  case db_ref_e:
+  default:
     RERROR();
   }
   RERROR();
@@ -425,7 +425,7 @@ p_or(Term t1, Term t2) {
 #ifdef USE_GMP
       return(Yap_gmp_ior_int_big(IntegerOfTerm(t1),Yap_BigIntOfTerm(t2)));
 #endif
-    case db_ref_e:
+    default:
       RERROR();
     }
     break;
@@ -442,11 +442,11 @@ p_or(Term t1, Term t2) {
       return Yap_gmp_ior_big_big(Yap_BigIntOfTerm(t2), Yap_BigIntOfTerm(t1));
     case double_e:
       return Yap_ArithError(TYPE_ERROR_INTEGER, t2, "\\/ /2");
-    case db_ref_e:
+    default:
       RERROR();
     }
 #endif
-  case db_ref_e:
+  default:
     RERROR();
   }
   RERROR();
@@ -473,7 +473,7 @@ p_sll(Term t1, Term t2) {
 #ifdef USE_GMP
       return Yap_ArithError(RESOURCE_ERROR_HUGE_INT, t2, "<</2");
 #endif
-    case db_ref_e:
+    default:
       RERROR();
     }
     break;
@@ -488,11 +488,11 @@ p_sll(Term t1, Term t2) {
       return Yap_ArithError(RESOURCE_ERROR_HUGE_INT, t2, ">>/2");
     case double_e:
       return Yap_ArithError(TYPE_ERROR_INTEGER, t2, "<</2");
-    case db_ref_e:
+    default:
       RERROR();
     }
 #endif
-  case db_ref_e:
+  default:
     RERROR();
   }
   RERROR();
@@ -519,7 +519,7 @@ p_slr(Term t1, Term t2) {
 #ifdef USE_GMP
       return Yap_ArithError(RESOURCE_ERROR_HUGE_INT, t2, ">>/2");
 #endif
-    case db_ref_e:
+    default:
       RERROR();
     }
     break;
@@ -534,11 +534,11 @@ p_slr(Term t1, Term t2) {
       return Yap_ArithError(RESOURCE_ERROR_HUGE_INT, t2, ">>/2");
     case double_e:
       return Yap_ArithError(TYPE_ERROR_INTEGER, t2, ">>/2");
-    case db_ref_e:
+    default:
       RERROR();
     }
 #endif
-  case db_ref_e:
+  default:
     RERROR();
   }
   RERROR();