diff --git a/src/h5core/h5b_model.c b/src/h5core/h5b_model.c
index 8bfa91d..6ff7b3c 100644
--- a/src/h5core/h5b_model.c
+++ b/src/h5core/h5b_model.c
@@ -45,7 +45,7 @@ _normalize_partition (
 	}
 }
 
-#if defined(PARALLEL)
+#ifdef PARALLEL_IO
 /* MLH: this could be improved with an MPI_Reduce and MAX operator...
  * but the user_layout array-of-structs would need to be a struct-of-arrays */
 static void
@@ -699,7 +699,7 @@ h5b_3d_get_chunk (
 	return H5_SUCCESS;
 }
 
-#if defined(PARALLEL_IO)
+#ifdef PARALLEL_IO
 h5_err_t
 h5b_3d_set_grid (
 	h5_file_t *const f,		/*!< IN: File handle */
diff --git a/src/include/H5Block.h b/src/include/H5Block.h
index 19f8013..d437094 100644
--- a/src/include/H5Block.h
+++ b/src/include/H5Block.h
@@ -69,9 +69,9 @@ h5_err_t
 H5Block3dGetGridCoords (
 	h5_file_t *const f,		/*!< IN: File handle */
 	const int proc,			/*!< IN: MPI processor */
-	h5_size_t *const i,		/*!< OUT: index in \c i */ 
-	h5_size_t *const j,		/*!< OUT: index in \c j */  
-	h5_size_t *const k		/*!< OUT: index in \c k */ 
+	h5_int64_t *const i,		/*!< OUT: index in \c i */ 
+	h5_int64_t *const j,		/*!< OUT: index in \c j */  
+	h5_int64_t *const k		/*!< OUT: index in \c k */ 
 	);
 
 h5_err_t
diff --git a/src/include/h5core/h5b_model.h b/src/include/h5core/h5b_model.h
index fa334fa..a62c93e 100644
--- a/src/include/h5core/h5b_model.h
+++ b/src/include/h5core/h5b_model.h
@@ -97,9 +97,9 @@ h5_err_t
 h5b_3d_get_grid_coords (
 	h5_file_t *const f,		/*!< IN: File handle */
 	const int proc,			/*!< IN: MPI processor */
-	h5_size_t *const i,		/*!< OUT: index in \c i */ 
-	h5_size_t *const j,		/*!< OUT: index in \c j */  
-	h5_size_t *const k		/*!< OUT: index in \c k */ 
+	h5_int64_t *const i,		/*!< OUT: index in \c i */ 
+	h5_int64_t *const j,		/*!< OUT: index in \c j */  
+	h5_int64_t *const k		/*!< OUT: index in \c k */ 
 	);
 
 h5_err_t