diff --git a/regtests/bin/matrix.base b/regtests/bin/matrix.base
index 88e7ee835..864583358 100755
--- a/regtests/bin/matrix.base
+++ b/regtests/bin/matrix.base
@@ -689,6 +689,7 @@
       echo "$rtst -s ST0 -w work_ST0 $ww3 ww3_tp2.6" >> matrix.body
       echo "$rtst -s ST0 -w work_ST0 $ww3 ww3_tp2.7" >> matrix.body
       echo "$rtst -s ST4 -w work_ST4 $ww3 ww3_tp2.6" >> matrix.body
+      echo "$rtst -s ST4_ASCII -w work_ST4_ASCII $ww3 ww3_tp2.6" >> matrix.body
     fi
 
     if [ "$prop1D" = 'y' ]
@@ -1885,6 +1886,7 @@
   then
     echo ' ' >> matrix.body
     echo "$rtst -s MPI -w work_MPI -m grdset_a -f -p $mpi -n $np $ww3 mww3_test_09" >> matrix.body
+    echo "$rtst -s MPI_ASCII -w work_MPI_ASCII -m grdset_a -f -p $mpi -n $np $ww3 mww3_test_09" >> matrix.body
   fi
 
 # Rotated pole grid cases, (ww3_tp2.11 MPI only if requested)
diff --git a/regtests/mww3_test_09/input/switch_MPI_ASCII b/regtests/mww3_test_09/input/switch_MPI_ASCII
new file mode 100644
index 000000000..e3d9628f0
--- /dev/null
+++ b/regtests/mww3_test_09/input/switch_MPI_ASCII
@@ -0,0 +1 @@
+ASCII NOGRB MPI DIST PR2 UNO SMC FLX2 LN0 ST0 NL0 BT0 DB0 TR0 BS0 IC0 IS0 REF0 WNT1 WNX1 CRT1 CRX1 O0 O1 O2 O3 O4 O5 O6 O7 O10 O11 
diff --git a/regtests/ww3_tp2.6/input/switch_ST4_ASCII b/regtests/ww3_tp2.6/input/switch_ST4_ASCII
new file mode 100644
index 000000000..db1b70b66
--- /dev/null
+++ b/regtests/ww3_tp2.6/input/switch_ST4_ASCII
@@ -0,0 +1 @@
+ASCII NOGRB SHRD PR3 UQ FLX0 LN0 ST4 NL1 BT1 DB1 MLIM TR0 BS0 IC0 IS0 REF0 WNT1 WNX1 CRT1 CRX1 O0 O1 O2 O3 O4 O5 O6 O7 O10 O11