diff --git a/common/command_line.cpp b/common/command_line.cpp
index 59a893731787..0c043c15c406 100644
--- a/common/command_line.cpp
+++ b/common/command_line.cpp
@@ -1039,7 +1039,8 @@ auto Parser::ParseShortOptionSeq(llvm::StringRef unparsed_arg)
     auto* arg_entry =
         (c < short_option_table_.size()) ? short_option_table_[c] : nullptr;
     if (!arg_entry) {
-      return Error(llvm::formatv("unknown short option `{0}`", c));
+      return Error(
+          llvm::formatv("unknown short option `-{0}`", static_cast<char>(c)));
     }
     // Mark this argument as parsed.
     arg_entry->setInt(true);
diff --git a/common/command_line_test.cpp b/common/command_line_test.cpp
index 2a45cb6817a5..1157aa8b9dc9 100644
--- a/common/command_line_test.cpp
+++ b/common/command_line_test.cpp
@@ -188,6 +188,10 @@ TEST(ArgParserTest, ShortArgs) {
   EXPECT_THAT(integer_option, Eq(123));
 
   TestRawOstream os;
+
+  EXPECT_THAT(parse({"-v"}, os), IsError(StrEq("unknown short option `-v`")));
+  EXPECT_THAT(parse({"-xvx"}, os), IsError(StrEq("unknown short option `-v`")));
+
   EXPECT_THAT(
       parse({"-xzf"}, os),
       IsError(StrEq("option `-z` (short for `--option2`) requires a value to "