diff --git a/PDP1/pdp1_stddev.c b/PDP1/pdp1_stddev.c
index 862814c6..255fdfe8 100644
--- a/PDP1/pdp1_stddev.c
+++ b/PDP1/pdp1_stddev.c
@@ -406,8 +406,10 @@ if (ptr_hold & CW) {                                    /* char waiting? */
     }
 else {
     for (;;) {                                          /* until valid char */
-        if ((c = getc (uptr->fileref)) == EOF)          /* get next char, EOF? */
+        if ((c = getc (uptr->fileref)) == EOF) {        /* get next char, EOF? */
+            ptr_leader = PTR_LEADER;                    /* set up for trailer */
             return FIODEC_STOP;                         /* return STOP */
+            }
         uptr->pos = uptr->pos + 1;                      /* count char */
         c = c & 0177;                                   /* cut to 7b */
         if (c == '\n')                                  /* NL -> CR */
@@ -532,11 +534,13 @@ if ((uptr->flags & UNIT_ATT) == 0)                      /* not attached? */
     return IORETURN (ptp_stopioe, SCPE_UNATT);
 if ((uptr->flags & UNIT_ASCII) != 0) {                  /* ASCII mode? */
     int32 c1 = uptr->buf & 077;
-    if (c1 == FIODEC_UC) {
+    if (uptr->buf == 0)                                 /* ignore nulls */
+        return SCPE_OK;
+    if (c1 == FIODEC_UC) {                              /* UC? absorb */
         ptp_uc = UC;
         return SCPE_OK;
         }
-    else if (c1 == FIODEC_LC) {
+    else if (c1 == FIODEC_LC) {                         /* LC? absorb */
         ptp_uc = 0;
         return SCPE_OK;
         }