diff --git a/src/c/array.d b/src/c/array.d
index 65122f453..7b54b3e9e 100644
--- a/src/c/array.d
+++ b/src/c/array.d
@@ -108,6 +108,9 @@ aref(cl_object x, cl_index index)
   case aet_fix:
     return make_integer(x->array.self.fix[index]);
 
+  case aet_index:
+    return make_unsigned_integer(x->array.self.index[index]);
+
   case aet_sf:
     return(make_shortfloat(x->array.self.sf[index]));
 
@@ -211,7 +214,11 @@ aset(cl_object x, cl_index index, cl_object value)
     break;
   }
   case aet_fix:
-    x->array.self.fix[index] = object_to_fixnum(value);
+    x->array.self.fix[index] = fixint(value);
+    break;
+
+  case aet_index:
+    x->array.self.index[index] = fixnnint(value);
     break;
 
   case aet_sf:
@@ -390,6 +397,14 @@ array_allocself(cl_object x)
 		x->array.self.fix = elts;
 		break;
 	      }
+	case aet_index: {
+		cl_fixnum *elts;
+		elts = (cl_fixnum *)cl_alloc_atomic_align(sizeof(*elts)*d, sizeof(*elts));
+		for (i = 0;  i < d;  i++)
+			elts[i] = 0;
+		x->array.self.fix = elts;
+		break;
+	      }
 	case aet_sf: {
 		float *elts;
 		elts = (float *)cl_alloc_atomic_align(sizeof(*elts)*d, sizeof(*elts));
@@ -436,6 +451,8 @@ ecl_symbol_to_elttype(cl_object x)
 		return(aet_bit);
 	else if (x == @'ext::cl-fixnum')
 		return(aet_fix);
+	else if (x == @'ext::cl-index')
+		return(aet_index);
 	else if (x == @'single-float' || x == @'short-float')
 		return(aet_sf);
 	else if (x == @'long-float' || x == @'double-float')
@@ -459,6 +476,7 @@ ecl_elttype_to_symbol(cl_elttype aet)
 	case aet_ch:		output = @'base-char'; break;
 	case aet_bit:		output = @'bit'; break;
 	case aet_fix:		output = @'ext::cl-fixnum'; break;
+	case aet_index:		output = @'ext::cl-index'; break;
 	case aet_sf:		output = @'short-float'; break;
 	case aet_lf:		output = @'long-float'; break;
 	case aet_b8:		output = @'ext::byte8'; break;
@@ -475,6 +493,8 @@ array_address(cl_object x, cl_index inc)
 		return x->array.self.t + inc;
 	case aet_fix:
 		return x->array.self.fix + inc;
+	case aet_index:
+		return x->array.self.fix + inc;
 	case aet_sf:
 		return x->array.self.t + inc;
 	case aet_ch:
@@ -679,6 +699,9 @@ cl_array_displacement(cl_object a)
 		case aet_fix:
 			offset = a->array.self.fix - to_array->array.self.fix;
 			break;
+		case aet_index:
+			offset = a->array.self.fix - to_array->array.self.fix;
+			break;
 		case aet_sf:
 			offset = a->array.self.sf - to_array->array.self.sf;
 			break;
diff --git a/src/c/sequence.d b/src/c/sequence.d
index 33692fc9b..07a4e2649 100644
--- a/src/c/sequence.d
+++ b/src/c/sequence.d
@@ -195,6 +195,7 @@ E:
 		switch ((cl_elttype)sequence->vector.elttype) {
 		case aet_object:
 		case aet_fix:
+		case aet_index:
 		case aet_sf:
 			for (i = s, j = 0;  i < e;  i++, j++)
 				x->vector.self.t[j] = sequence->vector.self.t[i];
@@ -325,6 +326,7 @@ cl_reverse(cl_object seq)
 		switch ((cl_elttype)x->vector.elttype) {
 		case aet_object:
 		case aet_fix:
+		case aet_index:
 		case aet_sf:
 			for (j = k - 1, i = 0;  j >=0;  --j, i++)
 				y->vector.self.t[j] = x->vector.self.t[i];
@@ -401,6 +403,7 @@ cl_nreverse(cl_object seq)
 		switch ((cl_elttype)x->vector.elttype) {
 		case aet_object:
 		case aet_fix:
+		case aet_index:
 			for (i = 0, j = k - 1;  i < j;  i++, --j) {
 				y = x->vector.self.t[i];
 				x->vector.self.t[i] = x->vector.self.t[j];
diff --git a/src/c/symbols_list.h b/src/c/symbols_list.h
index c08f8f011..c9b3cee9c 100644
--- a/src/c/symbols_list.h
+++ b/src/c/symbols_list.h
@@ -1525,6 +1525,7 @@ cl_symbols[] = {
 
 {SYS_ "CL-FIXNUM-BITS", SI_CONSTANT, NULL, -1, MAKE_FIXNUM(FIXNUM_BITS)},
 {EXT_ "CL-FIXNUM", SI_ORDINARY, NULL, -1, NULL},
+{EXT_ "CL-INDEX", SI_ORDINARY, NULL, -1, NULL},
 
 /* Tag for end of list */
 {NULL, CL_ORDINARY, NULL, -1, OBJNULL}};
diff --git a/src/c/symbols_list2.h b/src/c/symbols_list2.h
index e0c5b6cfd..bcb0fe67a 100644
--- a/src/c/symbols_list2.h
+++ b/src/c/symbols_list2.h
@@ -1525,6 +1525,7 @@ cl_symbols[] = {
 
 {SYS_ "CL-FIXNUM-BITS",NULL},
 {EXT_ "CL-FIXNUM",NULL},
+{EXT_ "CL-INDEX",NULL},
 
 /* Tag for end of list */
 {NULL,NULL}};
diff --git a/src/h/object.h b/src/h/object.h
index c7d24d9db..ddd0771fc 100644
--- a/src/h/object.h
+++ b/src/h/object.h
@@ -206,7 +206,8 @@ typedef enum {			/*  array element type  */
 	aet_sf,			/*  short-float      */
 	aet_lf,			/*  long-float       */
 	aet_bit,		/*  bit              */
-	aet_fix,		/*  fixnum           */
+	aet_fix,		/*  cl_fixnum        */
+	aet_index,		/*  cl_index         */
 	/* Below here, list types accepted by streams (i.e. OPEN) */
 	aet_b8,			/*  byte8	     */
 	aet_i8,			/*  integer8	     */
@@ -221,6 +222,7 @@ union ecl_array_data {
 	float *sf;
 	double *lf;
 	cl_fixnum *fix;
+	cl_index *index;
 	byte *bit;
 };
 
diff --git a/src/lsp/predlib.lsp b/src/lsp/predlib.lsp
index dc92c4a40..6125792c4 100644
--- a/src/lsp/predlib.lsp
+++ b/src/lsp/predlib.lsp
@@ -58,6 +58,7 @@ bignums."
 (deftype ext::byte8 () `(INTEGER 0 255))
 (deftype ext::integer8 () `(INTEGER -128 127))
 (deftype ext::cl-fixnum () `(SIGNED-BYTE #.CL-FIXNUM-BITS))
+(deftype ext::cl-index () `(UNSIGNED-BYTE #.CL-FIXNUM-BITS))
 
 (deftype real (&rest foo) '(OR RATIONAL FLOAT))
 
@@ -214,7 +215,7 @@ has no fill-pointer, and is not adjustable."
   (put-sysprop (car l) 'TYPE-PREDICATE (cdr l)))
 
 (defconstant +upgraded-array-element-types+
-  '(BASE-CHAR BIT EXT::BYTE8 EXT::INTEGER8 EXT::CL-FIXNUM SHORT-FLOAT LONG-FLOAT T))
+  '(BASE-CHAR BIT EXT::BYTE8 EXT::INTEGER8 EXT::CL-FIXNUM EXT::CL-INDEX SHORT-FLOAT LONG-FLOAT T))
 
 (defun upgraded-array-element-type (element-type &optional env)
   (dolist (v +upgraded-array-element-types+ 'T)
@@ -1063,6 +1064,7 @@ if not possible."
 	       ((VECTOR EXT::BYTE8) (ARRAY EXT::BYTE8 (*)))
 	       ((VECTOR EXT::INTEGER8) (ARRAY EXT::INTEGER8 (*)))
 	       ((VECTOR EXT::CL-FIXNUM) (ARRAY EXT::CL-FIXNUM (*)))
+	       ((VECTOR EXT::CL-INDEX) (ARRAY EXT::CL-INDEX (*)))
 	       ((VECTOR SHORT-FLOAT) (ARRAY SHORT-FLOAT (*)))
 	       ((VECTOR LONG-FLOAT) (ARRAY LONG-FLOAT (*)))
 	       ((VECTOR T) (ARRAY T (*)))