diff --git a/C/atomic.c b/C/atomic.c
index 354ae5d84..10e39e909 100644
--- a/C/atomic.c
+++ b/C/atomic.c
@@ -661,26 +661,31 @@ static Int atom_concat3(USES_REGS1) {
   Term t1;
   Term t2, t3, ot;
   Atom at;
+  bool g1, g2, g3;
 restart_aux:
   t1 = Deref(ARG1);
   t2 = Deref(ARG2);
   t3 = Deref(ARG3);
-  if (Yap_IsGroundTerm(t1) && Yap_IsGroundTerm(t2)) {
+  g1 = Yap_IsGroundTerm(t1); 
+  g2 = Yap_IsGroundTerm(t2); 
+  g3 = Yap_IsGroundTerm(t3); 
+  if (g1 && g2) {
     at = Yap_ConcatAtoms(t1, t2 PASS_REGS);
     ot = ARG3;
-  } else if (Yap_IsGroundTerm(t1) && Yap_IsGroundTerm(t3)) {
-    at = Yap_SubtractHeadAtom(Deref(ARG3), t1 PASS_REGS);
+  } else if (g1 && g3) {
+    at = Yap_SubtractHeadAtom(t3, t1 PASS_REGS);
     ot = ARG2;
-  } else if (Yap_IsGroundTerm(t2) && Yap_IsGroundTerm(t3)) {
-    at = Yap_SubtractTailAtom(Deref(ARG3), t2 PASS_REGS);
+  } else if (g2 && g3) {
+    at = Yap_SubtractTailAtom(t3, t2 PASS_REGS);
          ot = ARG1;
-  } else if (Yap_IsGroundTerm(t3)) {
+  } else if (g3) {
     EXTRA_CBACK_ARG(3, 1) = MkIntTerm(0);
     EXTRA_CBACK_ARG(3, 2) = MkIntTerm(Yap_AtomToLength(t3 PASS_REGS));
     return cont_atom_concat3(PASS_REGS1);
   } else {
       LOCAL_Error_TYPE = INSTANTIATION_ERROR;
       LOCAL_Error_Term = t1;
+      at = NULL;
   }
   if (at) {
     if (Yap_unify(ot, MkAtomTerm(at)))
@@ -693,7 +698,7 @@ restart_aux:
     if (Yap_HandleError("atom_concat/3")) {
       goto restart_aux;
     } else {
-      return FALSE;
+      return false;
     }
   }
   cut_fail();
@@ -751,29 +756,34 @@ static Int atomic_concat3(USES_REGS1) {
   Term t1;
   Term t2, t3, ot;
   Atom at = NULL;
+  bool g1, g2, g3;
 restart_aux:
   t1 = Deref(ARG1);
   t2 = Deref(ARG2);
   t3 = Deref(ARG3);
-  if (Yap_IsGroundTerm(t1) && Yap_IsGroundTerm(t2)) {
-    at = Yap_ConcatAtoms(CastToAtom(t1), CastToAtom(t2) PASS_REGS);
+  g1 = Yap_IsGroundTerm(t1); 
+  g2 = Yap_IsGroundTerm(t2); 
+  g3 = Yap_IsGroundTerm(t3); 
+  if (g1 && g2) {
+    at = Yap_ConcatAtomics(t1, t2 PASS_REGS);
     ot = ARG3;
-  } else if (Yap_IsGroundTerm(t1) && Yap_IsGroundTerm(t3)) {
-    at = Yap_SubtractHeadAtom(t3, CastToAtom(t1) PASS_REGS);
+  } else if (g1 && g3) {
+    at = Yap_SubtractHeadAtom(t3, t1 PASS_REGS);
     ot = ARG2;
-  } else if (Yap_IsGroundTerm(t2) && Yap_IsGroundTerm(t3)) {
-    at = Yap_SubtractTailAtom(t3, CastToAtom(t2) PASS_REGS);
-    ot = ARG1;
-  } else if (Yap_IsGroundTerm(t3)) {
+  } else if (g2 && g3) {
+    at = Yap_SubtractTailAtom(t3, t2 PASS_REGS);
+         ot = ARG1;
+  } else if (g3) {
     EXTRA_CBACK_ARG(3, 1) = MkIntTerm(0);
     EXTRA_CBACK_ARG(3, 2) = MkIntTerm(Yap_AtomicToLength(t3 PASS_REGS));
     return cont_atomic_concat3(PASS_REGS1);
   } else {
-    LOCAL_Error_TYPE = INSTANTIATION_ERROR;
-    LOCAL_Error_Term = t1;
+      LOCAL_Error_TYPE = INSTANTIATION_ERROR;
+      LOCAL_Error_Term = t1;
+      at = NULL;
   }
   if (at) {
-    if (Yap_unify(ot, CastToNumeric(at)))
+    if (Yap_unify(ot, MkAtomTerm(at)))
       cut_succeed();
     else
       cut_fail();
@@ -783,7 +793,7 @@ restart_aux:
     if (Yap_HandleError("atomic_concat/3")) {
       goto restart_aux;
     } else {
-      return FALSE;
+      return false;
     }
   }
   cut_fail();
@@ -822,40 +832,45 @@ static Int string_concat3(USES_REGS1) {
   Term t1;
   Term t2, t3, ot;
   Term tf = 0;
+  bool g1, g2, g3;
+  Atom at;
 restart_aux:
   t1 = Deref(ARG1);
   t2 = Deref(ARG2);
   t3 = Deref(ARG3);
-  if (Yap_IsGroundTerm(t1) && Yap_IsGroundTerm(t2)) {
+  g1 = Yap_IsGroundTerm(t1); 
+  g2 = Yap_IsGroundTerm(t2); 
+  g3 = Yap_IsGroundTerm(t3); 
+  if (g1 && g2) {
     tf = Yap_ConcatStrings(t1, t2 PASS_REGS);
     ot = ARG3;
-  } else if (Yap_IsGroundTerm(t1) && Yap_IsGroundTerm(t3)) {
+  } else if (g1 && g3) {
     tf = Yap_SubtractHeadString(t3, t1 PASS_REGS);
     ot = ARG2;
-  } else if (Yap_IsGroundTerm(t2) && Yap_IsGroundTerm(t3)) {
+  } else if (g2 && g3) {
     tf = Yap_SubtractTailString(t3, t2 PASS_REGS);
-    ot = ARG1;
-  } else if (Yap_IsGroundTerm(t3)) {
+         ot = ARG1;
+  } else if (g3) {
     EXTRA_CBACK_ARG(3, 1) = MkIntTerm(0);
     EXTRA_CBACK_ARG(3, 2) = MkIntTerm(Yap_StringToLength(t3 PASS_REGS));
     return cont_string_concat3(PASS_REGS1);
   } else {
-    LOCAL_Error_TYPE = INSTANTIATION_ERROR;
-    LOCAL_Error_Term = t1;
+      LOCAL_Error_TYPE = INSTANTIATION_ERROR;
+      LOCAL_Error_Term = t1;
+      at = NULL;
   }
   if (tf) {
-    if (Yap_unify(ot, tf)) {
+    if (Yap_unify(ot, tf))
       cut_succeed();
-    } else {
+    else
       cut_fail();
-    }
   }
   /* Error handling */
   if (LOCAL_Error_TYPE) {
-    if (Yap_HandleError("string_concat/3")) {
+    if (Yap_HandleError("atom_concat/3")) {
       goto restart_aux;
     } else {
-      return FALSE;
+      return false;
     }
   }
   cut_fail();
diff --git a/C/text.c b/C/text.c
index a71d46679..cecff54cc 100644
--- a/C/text.c
+++ b/C/text.c
@@ -104,6 +104,7 @@ static Int SkipListCodes(unsigned char **bufp, Term *l, Term **tailp,
     *bufp = st = st0;
 
     if (*l == TermNil) {
+      st[0] = '\0';
         return 0;
     }
     if (IsPairTerm(*l)) {
@@ -311,7 +312,7 @@ unsigned char *Yap_readText(seq_tv_t *inp, size_t *lengp) {
             } else if (!IsStringTerm(inp->val.t) &&
                        inp->type == YAP_STRING_STRING) {
                 LOCAL_Error_TYPE = TYPE_ERROR_STRING;
-            } else if (!IsPairTerm(inp->val.t) && !IsStringTerm(inp->val.t) &&
+            } else if (!IsPairOrNilTerm(inp->val.t) && !IsStringTerm(inp->val.t) &&
                        inp->type ==
                        (YAP_STRING_ATOMS_CODES | YAP_STRING_STRING)) {
                 LOCAL_Error_TYPE = TYPE_ERROR_LIST;
@@ -344,20 +345,20 @@ unsigned char *Yap_readText(seq_tv_t *inp, size_t *lengp) {
        return UStringOfTerm(inp->val.t);
       }
     if (((inp->type & (YAP_STRING_CODES | YAP_STRING_ATOMS)) ==
-         (YAP_STRING_CODES | YAP_STRING_ATOMS)) && IsPairTerm(inp->val.t)) {
+         (YAP_STRING_CODES | YAP_STRING_ATOMS)) && IsPairOrNilTerm(inp->val.t)) {
         //Yap_DebugPlWriteln(inp->val.t);
         return inp->val.uc =
                        Yap_ListToBuffer(s0, inp->val.t, inp, &wide, lengp
                                         PASS_REGS);
         // this is a term, extract to a sfer, and representation is wide
     }
-    if (inp->type & YAP_STRING_CODES && IsPairTerm(inp->val.t)) {
+    if (inp->type & YAP_STRING_CODES && IsPairOrNilTerm(inp->val.t)) {
         //Yap_DebugPlWriteln(inp->val.t);
         return inp->val.uc = Yap_ListOfCodesToBuffer(s0, inp->val.t, inp, &wide,
                                                      lengp PASS_REGS);
         // this is a term, extract to a sfer, and representation is wide
     }
-    if (inp->type & YAP_STRING_ATOMS && IsPairTerm(inp->val.t)) {
+    if (inp->type & YAP_STRING_ATOMS && IsPairOrNilTerm(inp->val.t)) {
         //Yap_DebugPlWriteln(inp->val.t);
         return inp->val.uc = Yap_ListOfAtomsToBuffer(s0, inp->val.t, inp, &wide,
                                                      lengp PASS_REGS);
@@ -1031,7 +1032,7 @@ const char *Yap_TextTermToText(Term t, char *buf, size_t len, encoding_t enc) {
     CACHE_REGS
     seq_tv_t inp, out;
     inp.val.t = t;
-    if (IsAtomTerm(t)) {
+    if (IsAtomTerm(t) && t != TermNil) {
         inp.type = YAP_STRING_ATOM;
         if (IsWideAtom(AtomOfTerm(t)))
             inp.enc = ENC_WCHAR;
@@ -1040,7 +1041,7 @@ const char *Yap_TextTermToText(Term t, char *buf, size_t len, encoding_t enc) {
     } else if (IsStringTerm(t)) {
         inp.type = YAP_STRING_STRING;
         inp.enc = ENC_ISO_UTF8;
-    } else if (IsPairTerm(t)) {
+    } else if (IsPairOrNilTerm(t)) {
         inp.type = (YAP_STRING_CODES | YAP_STRING_ATOMS);
     } else {
         Yap_Error(TYPE_ERROR_TEXT, t, NULL);
diff --git a/H/YapTags.h b/H/YapTags.h
index d2b446755..4ae7f2e06 100644
--- a/H/YapTags.h
+++ b/H/YapTags.h
@@ -350,4 +350,14 @@ INLINE_ONLY inline EXTERN void *AddressOfTerm(Term t) {
   return (void *)(IsIntTerm(t) ? IntOfTerm(t) : LongIntOfTerm(t));
 }
 
+
+INLINE_ONLY inline EXTERN Int IsPairTermOrNil (Term);
+
+INLINE_ONLY inline EXTERN Int
+IsPairOrNilTerm (Term t)
+{
+  return IsPairTerm(t) || t == TermNil;
+}
+
+
 #endif