diff --git a/gcc/fortran/simplify.c b/gcc/fortran/simplify.c
index abc3383..b744a21 100644
--- a/gcc/fortran/simplify.c
+++ b/gcc/fortran/simplify.c
@@ -6189,7 +6189,7 @@ gfc_simplify_image_index (gfc_expr *coarray, gfc_expr *sub)
   int d;
 
   if (!is_constant_array_expr (sub))
-    goto not_implemented; /* return NULL;*/
+    return NULL;
 
   /* Follow any component references.  */
   as = coarray->symtree->n.sym->as;
@@ -6198,7 +6198,7 @@ gfc_simplify_image_index (gfc_expr *coarray, gfc_expr *sub)
       as = ref->u.ar.as;
 
   if (as->type == AS_DEFERRED)
-    goto not_implemented; /* return NULL;*/
+    return NULL;
 
   /* "valid sequence of cosubscripts" are required; thus, return 0 unless
      the cosubscript addresses the first image.  */
@@ -6221,7 +6221,7 @@ gfc_simplify_image_index (gfc_expr *coarray, gfc_expr *sub)
       ca_bound = simplify_bound_dim (coarray, NULL, d + as->rank, 0, as,
 				     NULL, true);
       if (ca_bound == NULL)
-	goto not_implemented; /* return NULL */
+	return NULL;
 
       if (ca_bound == &gfc_bad_expr)
 	return ca_bound;
@@ -6285,6 +6285,10 @@ gfc_simplify_image_index (gfc_expr *coarray, gfc_expr *sub)
       return &gfc_bad_expr;
     }
 
+
+  if (gfc_option.coarray != GFC_FCOARRAY_SINGLE && !first_image)
+    return NULL;
+
   result = gfc_get_constant_expr (BT_INTEGER, gfc_default_integer_kind,
 				  &gfc_current_locus);
   if (first_image)
@@ -6293,11 +6297,6 @@ gfc_simplify_image_index (gfc_expr *coarray, gfc_expr *sub)
     mpz_set_si (result->value.integer, 0);
 
   return result;
-
-not_implemented:
-  gfc_error ("Not yet implemented: IMAGE_INDEX for coarray with non-constant "
-	     "cobounds at %L", &coarray->where);
-  return &gfc_bad_expr;
 }
 
 
diff --git a/gcc/fortran/trans-intrinsic.c b/gcc/fortran/trans-intrinsic.c
index b4cc360..9853686 100644
--- a/gcc/fortran/trans-intrinsic.c
+++ b/gcc/fortran/trans-intrinsic.c
@@ -929,6 +929,60 @@ trans_this_image (gfc_se * se, gfc_expr *expr ATTRIBUTE_UNUSED)
 }
 
 static void
+trans_image_index (gfc_se * se, gfc_expr *expr ATTRIBUTE_UNUSED)
+{
+  tree num_images, cond, coindex, type, lbound, desc;
+  gfc_se argse;
+  gfc_ss *ss;
+  int rank, corank;
+
+  type = gfc_get_int_type (gfc_default_integer_kind);
+  corank = gfc_get_corank (expr->value.function.actual->expr);
+  rank = expr->value.function.actual->expr->rank;
+
+  gfc_init_se (&argse, NULL);
+  ss = gfc_walk_expr (expr->value.function.actual->expr);
+  gcc_assert (ss != gfc_ss_terminator);
+  argse.want_pointer = 1;
+  argse.data_not_needed = 1;
+  gfc_conv_expr_descriptor (&argse, expr->value.function.actual->expr, ss);
+  gfc_add_block_to_block (&se->pre, &argse.pre);
+  gfc_add_block_to_block (&se->post, &argse.post);
+  desc = argse.expr;
+
+  /* See Fortran 2008, C.10 for the algorithm.  */
+
+  /* coindex = sub(corank) - lcobound(n).  */
+  coindex = NULL_TREE; /*FIXME: Use algorithm.  */
+  lbound = gfc_conv_descriptor_lbound_get (desc,
+			build_int_cst (gfc_array_index_type, rank+corank-1));
+  coindex = lbound;
+
+/*
+  for (codim = corank + rank - 2; codim >= rank; codim--)
+    {
+*/      /* coindex = coindex*extend(codim) + sub(codim) - lcobound(codim).  */
+/*      gfc_conv_descriptor_cosize (desc, codim, codim)
+    }
+*/
+  coindex = fold_build2_loc (input_location, PLUS_EXPR, type,
+			     coindex, build_int_cst (type, 1));
+
+  if (gfc_option.coarray == GFC_FCOARRAY_SINGLE)
+    num_images = build_int_cst (type, 0);
+  else
+    {
+      gfc_init_coarray_decl ();
+      num_images = gfort_gvar_caf_num_images;
+    }
+
+  cond = fold_build2_loc (input_location, LE_EXPR, boolean_type_node, coindex,
+			  num_images);
+  se->expr = fold_build3_loc (input_location, COND_EXPR, type, cond, coindex,
+			      build_int_cst (type, 0));
+}
+
+static void
 trans_num_images (gfc_se * se)
 {
   gfc_init_coarray_decl ();
@@ -6316,6 +6370,9 @@ gfc_conv_intrinsic_function (gfc_se * se, gfc_expr * expr)
 	trans_this_image (se, expr);
       break;
 
+    case GFC_ISYM_IMAGE_INDEX:
+      trans_image_index (se, expr);
+
     case GFC_ISYM_NUM_IMAGES:
       trans_num_images (se);
       break;