diff --git a/elf/cmdline.cc b/elf/cmdline.cc
index f22c2f62..37dd39c7 100644
--- a/elf/cmdline.cc
+++ b/elf/cmdline.cc
@@ -618,14 +618,13 @@ std::vector<std::string> parse_nonpositional_args(Context<E> &ctx) {
       ctx.arg.directory = arg;
     } else if (read_arg("chroot")) {
       ctx.arg.chroot = arg;
-    } else if (read_flag("color-diagnostics=auto")) {
+    } else if (read_flag("color-diagnostics") ||
+               read_flag("color-diagnostics=auto")) {
       ctx.arg.color_diagnostics = isatty(STDERR_FILENO);
     } else if (read_flag("color-diagnostics=always")) {
       ctx.arg.color_diagnostics = true;
     } else if (read_flag("color-diagnostics=never")) {
       ctx.arg.color_diagnostics = false;
-    } else if (read_flag("color-diagnostics")) {
-      ctx.arg.color_diagnostics = true;
     } else if (read_flag("warn-common")) {
       ctx.arg.warn_common = true;
     } else if (read_flag("no-warn-common")) {
diff --git a/test/elf/color-diagnostics.sh b/test/elf/color-diagnostics.sh
index 04fff238..35d4bf31 100755
--- a/test/elf/color-diagnostics.sh
+++ b/test/elf/color-diagnostics.sh
@@ -20,7 +20,7 @@ int main() { foo(); }
 EOF
 
 ! "$mold" -o $t/exe $t/a.o --color-diagnostics 2> $t/log
-grep -q $'\033' $t/log
+! grep -q $'\033' $t/log || false
 
 ! "$mold" -o $t/exe $t/a.o --color-diagnostics=always 2> $t/log
 grep -q $'\033' $t/log