diff --git a/nmap.cc b/nmap.cc
index 0e2723c8b..5db435975 100644
--- a/nmap.cc
+++ b/nmap.cc
@@ -802,7 +802,8 @@ void parse_options(int argc, char **argv) {
           o.randomize_hosts = 1;
           o.ping_group_sz = PING_GROUP_SZ * 4;
         } else if (optcmp(long_options[option_index].name, "nsock-engine") == 0) {
-          nsock_set_default_engine(optarg);
+          if (nsock_set_default_engine(optarg) < 0)
+            fatal("Unknown or non-available engine: %s", optarg);
         } else if (optcmp(long_options[option_index].name, "osscan-limit")  == 0) {
           o.osscan_limit = 1;
         } else if (optcmp(long_options[option_index].name, "osscan-guess")  == 0
diff --git a/nsock/include/nsock.h b/nsock/include/nsock.h
index ccb1431dd..134810e35 100644
--- a/nsock/include/nsock.h
+++ b/nsock/include/nsock.h
@@ -201,8 +201,10 @@ nsock_ssl_ctx nsp_ssl_init_max_speed(nsock_pool ms_pool);
  * strup()'ed by the library. No validity check is performed by this function,
  * beware nsp_new() will fatal() if an invalid/unavailable engine name was
  * supplied before.
- * Pass NULL to reset to default (use most efficient engine available). */
-void nsock_set_default_engine(char *engine);
+ * Pass NULL to reset to default (use most efficient engine available).
+ *
+ * Function returns 0 on success and -1 on error. */
+int nsock_set_default_engine(char *engine);
 
 /* Get a comma-separated list of available engines. */
 const char *nsock_list_engines(void);
diff --git a/nsock/src/nsock_engines.c b/nsock/src/nsock_engines.c
index 1adead059..902e9c599 100644
--- a/nsock/src/nsock_engines.c
+++ b/nsock/src/nsock_engines.c
@@ -107,7 +107,7 @@ struct io_engine *get_io_engine(void) {
   return engine;
 }
 
-void nsock_set_default_engine(char *engine) {
+int nsock_set_default_engine(char *engine) {
   if (engine_hint)
     free(engine_hint);
 
@@ -117,15 +117,15 @@ void nsock_set_default_engine(char *engine) {
     for (i = 0; available_engines[i] != NULL; i++) {
       if (strcmp(engine, available_engines[i]->name) == 0) {
         engine_hint = strdup(engine);
-        return;
+        return 0;
       }
     }
-    fatal("Unknown or non-available IO engine: %s\n", engine);
-  } else {
-    /* having engine = NULL is fine. This is actually the
-     * way to tell nsock to use the default engine again. */
-    engine_hint = NULL;
+    return -1;
   }
+  /* having engine = NULL is fine. This is actually the
+   * way to tell nsock to use the default engine again. */
+  engine_hint = NULL;
+  return 0;
 }
 
 const char *nsock_list_engines(void) {