diff --git a/src/util/argparser.cpp b/src/util/argparser.cpp
index d076661..148e557 100644
--- a/src/util/argparser.cpp
+++ b/src/util/argparser.cpp
@@ -51,6 +51,9 @@ void ArgParser::printOptionError(const char* name, Error error, bool longName)
 			printf("%s: option requires an argument -- '%s'\n", m_name, name);
 		}
 	}
+	else if (error == Error::InvalidArgumentType) {
+		printf("%s: invalid argument type '%s'\n", m_name, name);
+	}
 
 	// TODO: Print command usage, if it's enabled.
 }
@@ -217,6 +220,9 @@ bool ArgParser::parseArgument(std::string_view argument)
 			m_argumentIndex++;
 			continue;
 		}
+		else {
+			printOptionError(argument.data(), Error::InvalidArgumentType);
+		}
 
 		break;
 	}
diff --git a/src/util/argparser.h b/src/util/argparser.h
index 0a44048..d195851 100644
--- a/src/util/argparser.h
+++ b/src/util/argparser.h
@@ -29,6 +29,7 @@ public:
 		ExtraOperand,       // For arguments
 		DoesntAllowArgument,
 		RequiresArgument,
+		InvalidArgumentType,
 	};
 
 	struct Option {