diff --git a/src/main.cpp b/src/main.cpp
index b9886c6c0d..793c4d19d2 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -14,7 +14,6 @@
 #include "lammps.h"
 
 #include "input.h"
-#include "mdi_interface.h"
 
 #include <cstdlib>
 #include <mpi.h>
@@ -27,6 +26,41 @@
 #include "exceptions.h"
 #endif
 
+// import real or dummy calls to MolSSI Driver Interface library
+#if defined(LMP_USER_MDI)
+
+// true interface to MDI
+#include <mdi.h>
+
+#else
+
+// dummy interface to MDI
+// needed for compiling when MDI is not installed
+
+typedef int MDI_Comm;
+static int MDI_Init(int *argc, char ***argv)
+{
+  return 0;
+}
+static int MDI_Initialized(int *flag)
+{
+  return 0;
+}
+static int MDI_MPI_get_world_comm(void *world_comm)
+{
+  return 0;
+}
+static int MDI_Plugin_get_argc(int *argc)
+{
+  return 0;
+}
+static int MDI_Plugin_get_argv(char ***argv)
+{
+  return 0;
+}
+
+#endif
+
 using namespace LAMMPS_NS;
 
 /* ----------------------------------------------------------------------
@@ -50,9 +84,9 @@ int main(int argc, char **argv)
   if (mdi_flag)
     if (MDI_MPI_get_world_comm(&lammps_comm)) MPI_Abort(MPI_COMM_WORLD, 1);
 
-  // enable trapping selected floating point exceptions.
-  // this uses GNU extensions and is only tested on Linux
-  // therefore we make it depend on -D_GNU_SOURCE, too.
+      // enable trapping selected floating point exceptions.
+      // this uses GNU extensions and is only tested on Linux
+      // therefore we make it depend on -D_GNU_SOURCE, too.
 
 #if defined(LAMMPS_TRAP_FPE) && defined(_GNU_SOURCE)
   fesetenv(FE_NOMASK_ENV);
diff --git a/src/mdi_interface.h b/src/mdi_interface.h
deleted file mode 100644
index 9c90663696..0000000000
--- a/src/mdi_interface.h
+++ /dev/null
@@ -1,37 +0,0 @@
-/* -*- c++ -*- ----------------------------------------------------------
-   LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
-   http://lammps.sandia.gov, Sandia National Laboratories
-   Steve Plimpton, sjplimp@sandia.gov
-
-   Copyright (2003) Sandia Corporation.  Under the terms of Contract
-   DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
-   certain rights in this software.  This software is distributed under
-   the GNU General Public License.
-
-   See the README file in the top-level LAMMPS directory.
-------------------------------------------------------------------------- */
-
-#ifndef LMP_MDI_INTERFACE_H
-#define LMP_MDI_INTERFACE_H
-
-#if defined(LMP_USER_MDI)
-
-// true interface to MDI
-// used when MDI is installed
-
-#include "mdi.h"
-
-#else
-
-// dummy interface to MDI
-// needed for compiling when MDI is not installed
-
-  typedef int MDI_Comm;
-  inline int MDI_Init(int* argc, char ***argv) {return 0;};
-  inline int MDI_Initialized(int* flag) {return 0;};
-  inline int MDI_MPI_get_world_comm(void* world_comm) {return 0;};
-  inline int MDI_Plugin_get_argc(int* argc) {return 0;};
-  inline int MDI_Plugin_get_argv(char*** argv) {return 0;};
-
-#endif
-#endif