diff --git a/nread.c b/nread.c
index e0ea5f07..8d742114 100644
--- a/nread.c
+++ b/nread.c
@@ -1075,8 +1075,10 @@ static int CommandDataCB(int handle, void *userData)
       if (pPtr[i] == '\r' || pPtr[i] == '\n') {
         self->state = SKIPTERM;
         if (!testAndInvokeInterrupt(self, handle)) {
-          status =
-              CostaTop(self->pCon->pStack, GetCharArray(self->command));
+          if (self->pCon->iProtocolID == 0 && CostaLocked(self->pCon->pStack))
+            status = 0;
+          else
+            status = CostaTop(self->pCon->pStack, GetCharArray(self->command));
           if (!status) {
             SCWrite(self->pCon, "ERROR: Busy", eError);
           }
@@ -1174,8 +1176,10 @@ static int ANETTelnetProcess(int handle, void *usData)
       case '\r':
       case '\n':
         if (!testAndInvokeInterrupt(self, handle)) {
-          status =
-              CostaTop(self->pCon->pStack, GetCharArray(self->command));
+          if (self->pCon->iProtocolID == 0 && CostaLocked(self->pCon->pStack))
+            status = 0;
+          else
+            status = CostaTop(self->pCon->pStack, GetCharArray(self->command));
           if (!status) {
             SCWrite(self->pCon, "ERROR: Busy", eError);
           }