diff --git a/ncat/ncat_main.c b/ncat/ncat_main.c
index 33f7577eb..bd55248da 100644
--- a/ncat/ncat_main.c
+++ b/ncat/ncat_main.c
@@ -414,7 +414,8 @@ int main(int argc, char *argv[])
                     bye("You can't specify more than one --proxy-auth.");
                 o.proxy_auth = Strdup(optarg);
             } else if (strcmp(long_options[option_index].name, "nsock-engine") == 0) {
-                nsock_set_default_engine(optarg);
+                if (nsock_set_default_engine(optarg) < 0)
+                    bye("Unknown or non-available engine: %s.", optarg);
             } else if (strcmp(long_options[option_index].name, "broker") == 0) {
                 o.broker = 1;
                 /* --broker implies --listen. */
diff --git a/nping/ArgParser.cc b/nping/ArgParser.cc
index ea8035032..a6df2dab1 100644
--- a/nping/ArgParser.cc
+++ b/nping/ArgParser.cc
@@ -956,8 +956,8 @@ char errstr[256];
         if( o.issetDisablePacketCapture() && o.disablePacketCapture()==true )
             outError(QT_2, "Warning: There is no point on specifying a BPF filter if you disable packet capture. BPF filter will be ignored.");
     } else if (optcmp(long_options[option_index].name, "nsock-engine") == 0){
-        nsock_set_default_engine(optarg);
-
+        if (nsock_set_default_engine(optarg) < 0)
+          outFatal(QT_3, "Unknown or non-available engine: %s", optarg);
     /* Output Options */
     } else if (optcmp(long_options[option_index].name, "quiet") == 0 ){
             o.setVerbosity(-4);