diff --git a/ompi/include/mpi.h.in b/ompi/include/mpi.h.in
index 8553db9fbcd..f9d21c636b1 100644
--- a/ompi/include/mpi.h.in
+++ b/ompi/include/mpi.h.in
@@ -776,6 +776,7 @@ enum {
  */
 #define MPI_T_PVAR_ALL_HANDLES ((MPI_T_pvar_handle) -1)
 #define MPI_T_PVAR_HANDLE_NULL ((MPI_T_pvar_handle) 0)
+#define MPI_T_PVAR_SESSION_NULL ((MPI_T_pvar_session) 0)
 #define MPI_T_CVAR_HANDLE_NULL ((MPI_T_cvar_handle) 0)
 
 /* MPI-2 specifies that the name "MPI_TYPE_NULL_DELETE_FN" (and all
diff --git a/ompi/mpi/tool/pvar_session_free.c b/ompi/mpi/tool/pvar_session_free.c
index 41aa3bef6b4..98ec4a98a94 100644
--- a/ompi/mpi/tool/pvar_session_free.c
+++ b/ompi/mpi/tool/pvar_session_free.c
@@ -23,14 +23,19 @@
 
 int MPI_T_pvar_session_free(MPI_T_pvar_session *session)
 {
+    int ret = MPI_SUCCESS;
+
     if (!mpit_is_initialized ()) {
         return MPI_T_ERR_NOT_INITIALIZED;
     }
 
-    if (NULL != *session) {
+    /* Check that this is a valid session */
+    if (MPI_T_PVAR_SESSION_NULL == *session) {
+        ret = MPI_T_ERR_INVALID_SESSION;
+    } else {
         OBJ_RELEASE(*session);
-        *session = NULL;
+        *session = MPI_T_PVAR_SESSION_NULL;
     }
 
-    return MPI_SUCCESS;
+    return ret;
 }