diff --git a/src/frontend/inp.c b/src/frontend/inp.c
index ecc7fdb8f..4a4118fda 100644
--- a/src/frontend/inp.c
+++ b/src/frontend/inp.c
@@ -66,6 +66,8 @@ extern void tprint(struct card *deck);
 
 static bool wantdegsim = FALSE;
 extern int prepare_degsim(struct card* deck);
+static bool wantplainsim = FALSE;
+extern int prepare_plainsim(struct card* deck);
 
 //void inp_source_recent(void);
 //void inp_mc_free(void);
@@ -1095,10 +1097,14 @@ inp_spsource(FILE *fp, bool comfile, char *filename, bool intfile)
 #endif
            /* If compatmode is de and degsim is set by command 'degsim',
               translate the netlist by removing the monitors and adding the
-              extra degradation elements. */
-           if (wantdegsim && newcompat.de) {
-               wantdegsim = FALSE;
-               prepare_degsim(deck);
+              extra degradation elements, e.g. instance parameters. */
+           if (newcompat.de) {
+               if (wantdegsim) {
+                   wantdegsim = FALSE;
+                   prepare_degsim(deck);
+               }
+               else if (wantplainsim)
+                   prepare_plainsim(deck);
            }
 
            /* Parsing the circuit 5.
@@ -2713,6 +2719,9 @@ void setdegsim(void) {
     wantdegsim = TRUE;
 }
 
+void setplainsim(void) {
+    wantplainsim = TRUE;
+}
 #ifdef REM_UNUSED
 /* Finally get rid of unused MOS models */
 static void rem_unused_mos_models(struct card* deck) {
diff --git a/src/frontend/inpcom.c b/src/frontend/inpcom.c
index 75a3f3b07..a4359d8fb 100644
--- a/src/frontend/inpcom.c
+++ b/src/frontend/inpcom.c
@@ -1127,13 +1127,18 @@ struct card *inp_readall(FILE *fp, const char *dir_name, const char* file_name,
         inp_check_syntax(working);
 
         /* collect .agemodel data, skip .agemodel if newcompat.de is not set */
-        readdegparams(working);
         if (newcompat.de) {
-            /* replace all [  ] by @, except for a instances */
-            remsqrbra(working);
-
-            /* Add degradation monitors to devices in X lines */
-            adddegmonitors(working);
+            int numdegmodels = readdegparams(working);
+            if (numdegmodels > 0) {
+                /* replace all [  ] by @, except for a instances */
+                remsqrbra(working);
+                /* Add degradation monitors to devices in X lines */
+                adddegmonitors(working);
+            }
+            else {
+                fprintf(stderr, "Warning: No valid agemodel data found, degradation sim not possible\n");
+                newcompat.de = FALSE; /* skip inp.c, 1101 prepare_degsim()*/
+            }
         }
 
         if (newcompat.lt && newcompat.a)