diff --git a/src/command_parser/flag.py b/src/command_parser/flag.py
index 8ddfa81..6aa9052 100644
--- a/src/command_parser/flag.py
+++ b/src/command_parser/flag.py
@@ -16,3 +16,9 @@ class Flag(Option):
         Toogle the flag
         """
         self.value = not self.value
+
+    def long(self) -> str:
+        """
+        Return long version of the option (--verbose, etc.)
+        """
+        return "--{long}".format(long=self.name)
diff --git a/src/command_parser/option.py b/src/command_parser/option.py
index 795e50e..ccf2d5d 100644
--- a/src/command_parser/option.py
+++ b/src/command_parser/option.py
@@ -35,9 +35,3 @@ class Option:
             return self.name[0]
         else:
             return self.single_char
-
-    def long(self) -> str:
-        """
-        Return long version of the option (--help=, --version=, etc.)
-        """
-        return "--{long}=".format(long=self.name)
diff --git a/src/command_parser/parser.py b/src/command_parser/parser.py
index ae8bc90..9d811ad 100644
--- a/src/command_parser/parser.py
+++ b/src/command_parser/parser.py
@@ -12,6 +12,7 @@ def parse(line: str, flags: list[Flag], values: list[Value]):
     elements = line.split(" ")
     index = 0
     while index < len(elements):
+        prev_index = index
         element = elements[index]
         logger.debug(
             _("parsing element {element}".format(element=element))
@@ -68,6 +69,11 @@ def parse(line: str, flags: list[Flag], values: list[Value]):
                     if value.long() == element[: len(value.long())]:
                         value.apply(element[len(value.long()) :])
                         index += 1
+            if index == prev_index:
+                logger.warning(_("unknown {element}, ignoring").format(
+                    element = element
+                ))
+                index += 1
         except IndexError:
             logger.warning(_("empty value"))
             index += 1
diff --git a/src/command_parser/value.py b/src/command_parser/value.py
index 6bcc89b..5140fd3 100644
--- a/src/command_parser/value.py
+++ b/src/command_parser/value.py
@@ -47,3 +47,9 @@ class Value(Option):
                         option=self.name,
                     )
                 )
+
+    def long(self) -> str:
+        """
+        Return long version of the option (--help=, --version=, etc.)
+        """
+        return "--{long}=".format(long=self.name)