diff --git a/src/run_mopac.F90 b/src/run_mopac.F90
index 0add104e..ba9c4c94 100644
--- a/src/run_mopac.F90
+++ b/src/run_mopac.F90
@@ -128,6 +128,12 @@ subroutine run_mopac
       numcal0 = numcal
       job_no0 = job_no
       step_num0 = step_num
+! other initialization to prevent hysteresis between API calls (add more as needed)
+      keywrd = ' '
+      keywrd_txt = ' '
+      keywrd_quoted = ' '
+      refkey = ' '
+      call summary("",-21) ! reset MOPAC's error handler
 !------------------------------------------------------------------------
       tore = ios + iop + iod
       call fbx                            ! Factorials and Pascal's triangle (pure constants)