diff --git a/optparse.h b/optparse.h
index 8d6c0a9..6e02a73 100644
--- a/optparse.h
+++ b/optparse.h
@@ -120,6 +120,7 @@ char *optparse_arg(struct optparse *options);
 #define OPTPARSE_MSG_INVALID "invalid option"
 #define OPTPARSE_MSG_MISSING "option requires an argument"
 #define OPTPARSE_MSG_TOOMANY "option takes no arguments"
+#define OPTPARSE_MSG_UNKNOWN "unknown error"
 
 static int
 optparse_error(struct optparse *options, const char *msg, const char *data)
@@ -259,8 +260,12 @@ optparse(struct optparse *options, const char *optstring)
         else
             options->optarg = 0;
         return option[0];
+    default: {
+        char str[2] = {0, 0};
+        str[0] = option[0];
+        return optparse_error(options, OPTPARSE_MSG_UNKNOWN, str);
+    }
     }
-    return 0;
 }
 
 OPTPARSE_API
@@ -390,8 +395,8 @@ optparse_long(struct optparse *options,
                 options->optarg = options->argv[options->optind];
                 if (options->optarg == 0)
                     return optparse_error(options, OPTPARSE_MSG_MISSING, name);
-                else
-                    options->optind++;
+
+                options->optind++;
             }
             return options->optopt;
         }