diff --git a/libos/src/ArgumentParser.cpp b/libos/src/ArgumentParser.cpp
index 775c808e..7dc9f22b 100644
--- a/libos/src/ArgumentParser.cpp
+++ b/libos/src/ArgumentParser.cpp
@@ -277,7 +277,7 @@ namespace os
             else { TRY(sb.format(" [%s]", arg.name.chars())); }
         }
 
-        if (m_vector_argument) sb.format("%s..."_sv, m_positional_args.size() ? "" : " ");
+        if (m_vector_argument) TRY(sb.format("%s..."_sv, m_positional_args.size() ? "" : " "));
 
         TRY(sb.add('\n'));