diff --git a/src/clib/pio_file.c b/src/clib/pio_file.c
index 67e35b18330..795d2f0466c 100644
--- a/src/clib/pio_file.c
+++ b/src/clib/pio_file.c
@@ -51,7 +51,8 @@ extern int event_num[2][NUM_EVENTS];
  * @ingroup PIO_open_file_c
  * @author Jim Edwards, Ed Hartnett
  */
-int PIOc_openfile(int iosysid, int *ncidp, int *iotype, const char *filename,
+int
+PIOc_openfile(int iosysid, int *ncidp, int *iotype, const char *filename,
                   int mode)
 {
     LOG((1, "PIOc_openfile iosysid %d *iotype %d filename %s mode %d", iosysid,
@@ -78,7 +79,8 @@ int PIOc_openfile(int iosysid, int *ncidp, int *iotype, const char *filename,
  * @ingroup PIO_open_file_c
  * @author Ed Hartnett
  */
-int PIOc_openfile2(int iosysid, int *ncidp, int *iotype, const char *filename,
+int
+PIOc_openfile2(int iosysid, int *ncidp, int *iotype, const char *filename,
                    int mode)
 {
     LOG((1, "PIOc_openfile2 iosysid %d *iotype %d filename %s mode %d", iosysid,
@@ -99,27 +101,23 @@ int PIOc_openfile2(int iosysid, int *ncidp, int *iotype, const char *filename,
  * @ingroup PIO_open_file_c
  * @author Ed Hartnett
  */
-int PIOc_open(int iosysid, const char *path, int mode, int *ncidp)
+int
+PIOc_open(int iosysid, const char *path, int mode, int *ncidp)
 {
     int iotype;
+    iosystem_desc_t *ios;  /* Pointer to io system information. */
+    int ret;
 
-    LOG((1, "PIOc_open iosysid = %d path = %s mode = %x", iosysid, path, mode));
+    LOG((1, "PIOc_open iosysid = %d path = %s mode = %x", iosysid, path,
+         mode));
 
-    /* Figure out the iotype. */
-    if (mode & NC_NETCDF4)
-    {
-        if (mode & NC_MPIIO || mode & NC_MPIPOSIX)
-            iotype = PIO_IOTYPE_NETCDF4P;
-        else
-            iotype = PIO_IOTYPE_NETCDF4C;
-    }
-    else
-    {
-        if (mode & NC_PNETCDF || mode & NC_MPIIO)
-            iotype = PIO_IOTYPE_PNETCDF;
-        else
-            iotype = PIO_IOTYPE_NETCDF;
-    }
+    /* Get the IO system info from the id. */
+    if (!(ios = pio_get_iosystem_from_id(iosysid)))
+        return pio_err(NULL, NULL, PIO_EBADID, __FILE__, __LINE__);
+
+    /* Find the IOTYPE from the mode flag. */
+    if ((ret = find_iotype_from_omode(mode, &iotype)))
+        return pio_err(ios, NULL, ret, __FILE__, __LINE__);
 
     /* Open the file. If the open fails, do not retry as serial
      * netCDF. Just return the error code. */
@@ -144,7 +142,8 @@ int PIOc_open(int iosysid, const char *path, int mode, int *ncidp)
  * @ingroup PIO_create_file_c
  * @author Jim Edwards, Ed Hartnett
  */
-int PIOc_createfile(int iosysid, int *ncidp, int *iotype, const char *filename,
+int
+PIOc_createfile(int iosysid, int *ncidp, int *iotype, const char *filename,
                     int mode)
 {
     iosystem_desc_t *ios;  /* Pointer to io system information. */
@@ -188,7 +187,8 @@ int PIOc_createfile(int iosysid, int *ncidp, int *iotype, const char *filename,
  * @ingroup PIO_create_file_c
  * @author Ed Hartnett
  */
-int PIOc_create(int iosysid, const char *filename, int cmode, int *ncidp)
+int
+PIOc_create(int iosysid, const char *filename, int cmode, int *ncidp)
 {
     int iotype;            /* The PIO IO type. */
 
@@ -219,7 +219,8 @@ int PIOc_create(int iosysid, const char *filename, int cmode, int *ncidp)
  * @ingroup PIO_close_file_c
  * @author Jim Edwards, Ed Hartnett
  */
-int PIOc_closefile(int ncid)
+int
+PIOc_closefile(int ncid)
 {
     iosystem_desc_t *ios;  /* Pointer to io system information. */
     file_desc_t *file;     /* Pointer to file information. */
@@ -318,7 +319,8 @@ int PIOc_closefile(int ncid)
  * @returns PIO_NOERR for success, error code otherwise.
  * @author Jim Edwards, Ed Hartnett
  */
-int PIOc_deletefile(int iosysid, const char *filename)
+int
+PIOc_deletefile(int iosysid, const char *filename)
 {
     iosystem_desc_t *ios;  /* Pointer to io system information. */
     int ierr = PIO_NOERR;  /* Return code from function calls. */
@@ -395,7 +397,8 @@ int PIOc_deletefile(int iosysid, const char *filename)
  * @ingroup PIO_sync_file_c
  * @author Jim Edwards, Ed Hartnett
  */
-int PIOc_sync(int ncid)
+int
+PIOc_sync(int ncid)
 {
     iosystem_desc_t *ios;  /* Pointer to io system information. */
     file_desc_t *file;     /* Pointer to file information. */
diff --git a/src/clib/pio_internal.h b/src/clib/pio_internal.h
index e2a0f432126..adc89f7159c 100644
--- a/src/clib/pio_internal.h
+++ b/src/clib/pio_internal.h
@@ -194,6 +194,9 @@ extern "C" {
     int PIOc_openfile_retry(int iosysid, int *ncidp, int *iotype, const char *filename, int mode,
                             int retry, int use_ext_ncid);
 
+    /* Give the mode flag from an open, determine the IOTYPE. */
+    int find_iotype_from_omode(int mode, int *iotype);
+
     /* Given PIO type, find MPI type and type size. */
     int find_mpi_type(int pio_type, MPI_Datatype *mpi_type, int *type_size);
 
diff --git a/src/clib/pioc_support.c b/src/clib/pioc_support.c
index 94790185690..f24129ebbe1 100644
--- a/src/clib/pioc_support.c
+++ b/src/clib/pioc_support.c
@@ -2364,6 +2364,40 @@ inq_file_metadata(file_desc_t *file, int ncid, int iotype, int *nvars, int **rec
     return PIO_NOERR;
 }
 
+/**
+ * Find the appropriate IOTYPE from mode flags to nc_open().
+ *
+ * @param mode the mode flag from nc_open().
+ * @param iotype pointer that gets the IOTYPE.
+ *
+ * @return 0 on success, error code otherwise.
+ * @author Ed Hartnett
+ */
+int
+find_iotype_from_omode(int mode, int *iotype)
+{
+    /* Check inputs. */
+    pioassert(iotype, "pointer to iotype must be provided", __FILE__, __LINE__);
+
+    /* Figure out the iotype. */
+    if (mode & NC_NETCDF4)
+    {
+        if (mode & NC_MPIIO || mode & NC_MPIPOSIX)
+            *iotype = PIO_IOTYPE_NETCDF4P;
+        else
+            *iotype = PIO_IOTYPE_NETCDF4C;
+    }
+    else
+    {
+        if (mode & NC_PNETCDF || mode & NC_MPIIO)
+            *iotype = PIO_IOTYPE_PNETCDF;
+        else
+            *iotype = PIO_IOTYPE_NETCDF;
+    }
+
+    return PIO_NOERR;
+}
+
 /**
  * Open an existing file using PIO library. This is an internal
  * function. Depending on the value of the retry parameter, a failed
@@ -2648,6 +2682,16 @@ PIOc_openfile_retry(int iosysid, int *ncidp, int *iotype, const char *filename,
         /* Return the PIO ncid to the user. */
         *ncidp = file->pio_ncid;
     }
+    else
+    {
+        /* Use the ncid passed in from the netCDF dispatch code. */
+        file->pio_ncid = *ncidp;
+
+        /* To prevent PIO from reusing the same ncid, if someone
+         * starting mingling netcdf integration PIO and regular PIO
+         * code. */
+        pio_next_ncid = file->pio_ncid + 1;
+    }
 
     /* Add this file to the list of currently open files. */
     pio_add_to_file_list(file);
diff --git a/src/ncint/ncintdispatch.c b/src/ncint/ncintdispatch.c
index 9150e9f8c45..317fdef9fe1 100644
--- a/src/ncint/ncintdispatch.c
+++ b/src/ncint/ncintdispatch.c
@@ -8,7 +8,13 @@
 #include "config.h"
 #include <stdlib.h>
 #include "ncintdispatch.h"
+#include "nc4dispatch.h"
+#include "nc4internal.h"
 #include "pio.h"
+#include "pio_internal.h"
+
+/** Default iosysid. */
+int diosysid;
 
 /* This is the dispatch object that holds pointers to all the
  * functions that make up the NCINT dispatch interface. */
@@ -129,27 +135,37 @@ NC_NCINT_finalize(void)
     return NC_NOERR;
 }
 
-/** Default iosysid. */
-int diosysid;
-
 #define TEST_VAL_42 42
 int
 NC_NCINT_open(const char *path, int mode, int basepe, size_t *chunksizehintp,
               void *parameters, const NC_Dispatch *dispatch, NC *nc_file)
 {
+    int iotype;
+    iosystem_desc_t *ios;  /* Pointer to io system information. */
     int ret;
-    nc_file->int_ncid = nc_file->ext_ncid;
+
+    LOG((1, "NC_NCINT_open path = %s mode = %x", path, mode));
+
+    /* Get the IO system info from the id. */
+    if (!(ios = pio_get_iosystem_from_id(diosysid)))
+        return pio_err(NULL, NULL, PIO_EBADID, __FILE__, __LINE__);
 
     /* Turn of NC_UDF0 in the mode flag. */
     mode = mode & ~NC_UDF0;
 
-    /* /\* Add necessary structs to hold netcdf-4 file data. *\/ */
-    /* if ((retval = nc4_nc4f_list_add(nc_file, path, mode))) */
-    /*     return retval; */
+    /* Find the IOTYPE from the mode flag. */
+    if ((ret = find_iotype_from_omode(mode, &iotype)))
+        return pio_err(ios, NULL, ret, __FILE__, __LINE__);
+
+    /* Add necessary structs to hold netcdf-4 file data. */
+    if ((ret = nc4_nc4f_list_add(nc_file, path, mode)))
+        return ret;
 
-    /* /\* Open the file with PIO. *\/ */
-    /* if ((ret = PIOc_open(diosysid, path, mode, &nc_file->ext_ncid))) */
-    /*     return ret; */
+    /* Open the file with PIO. Tell openfile_retry to accept the
+     * externally assigned ncid. */
+    if ((ret = PIOc_openfile_retry(diosysid, &nc_file->ext_ncid, &iotype,
+                                   path, mode, 0, 1)))
+        return ret;
 
     return NC_NOERR;
 }
diff --git a/tests/ncint/tst_pio_udf.c b/tests/ncint/tst_pio_udf.c
index 0d2d80cc8f8..caa43b8c384 100644
--- a/tests/ncint/tst_pio_udf.c
+++ b/tests/ncint/tst_pio_udf.c
@@ -51,14 +51,8 @@ main(int argc, char **argv)
         PIOc_set_log_level(3);
 
         /* Open file with our defined functions. */
-        /* if (nc_open(FILE_NAME, NC_UDF0, &ncid)) ERR; */
-        /* if (nc_close(ncid)) ERR; */
-
-        /* /\* Open file again and abort, which is the same as closing it. *\/ */
-        /* if (nc_open(FILE_NAME, NC_UDF0, &ncid)) ERR; */
-        /* if (nc_inq_format(ncid, NULL) != TEST_VAL_42) ERR; */
-        /* if (nc_inq_format_extended(ncid, NULL, NULL) != TEST_VAL_42) ERR; */
-        /* if (nc_abort(ncid) != TEST_VAL_42) ERR; */
+        if (nc_open(FILE_NAME, NC_UDF0, &ncid)) ERR;
+        if (nc_close(ncid)) ERR;
 
         /* Close the iosystem. */
         if (nc_free_iosystem(iosysid)) ERR;