diff --git a/MANIFEST b/MANIFEST
index 13324dc..e77ce8f 100644
--- a/MANIFEST
+++ b/MANIFEST
@@ -58,6 +58,7 @@ t/Net-ACME2-Challenge-dns_account_01.t
 t/Net-ACME2-Challenge-http_01-Handler.t
 t/Net-ACME2-Challenge-tls_alpn_01.t
 t/Net-ACME2-Challenge.t
+t/Net-ACME2-Curl.t
 t/Net-ACME2-EAB.t
 t/Net-ACME2-Error.t
 t/Net-ACME2-get-certificate-guard.t
diff --git a/lib/Net/ACME2/Curl.pm b/lib/Net/ACME2/Curl.pm
index 39d62fe..1edc44c 100644
--- a/lib/Net/ACME2/Curl.pm
+++ b/lib/Net/ACME2/Curl.pm
@@ -46,6 +46,7 @@ use Net::Curl::Easy ();
 
 use Net::ACME2 ();
 use Net::ACME2::HTTP::Convert ();
+use Net::ACME2::X ();
 
 use constant _HTTP_TINY_INTERNAL_EXCEPTION_REASON => 'Internal Exception';
 
@@ -159,8 +160,7 @@ sub _imitate_http_tiny {
                 $reason = $1;
             }
             else {
-                $reason = q<>;
-                warn "Unparsable first header line: [$line]\n";
+                die Net::ACME2::X->create('Generic', "Unparsable first header line: [$line]");
             }
         }
     }
diff --git a/t/Net-ACME2-Curl.t b/t/Net-ACME2-Curl.t
new file mode 100644
index 0000000..f0cfb3b
--- /dev/null
+++ b/t/Net-ACME2-Curl.t
@@ -0,0 +1,98 @@
+#!/usr/bin/env perl
+
+use strict;
+use warnings;
+
+use Test::More;
+use Test::Exception;
+
+# _imitate_http_tiny is not exported, so we call it via full package name.
+# Net::ACME2::Curl requires Net::Curl::Easy (optional XS dep) at compile
+# time, so skip the entire test when it is not installed.
+
+use Net::ACME2::X;
+
+BEGIN {
+    eval { require Net::ACME2::Curl; 1 }
+        or plan skip_all => 'Net::Curl::Easy not available';
+}
+
+# Minimal mock that stands in for a Net::Curl::Easy instance.
+{
+    package    # hide from PAUSE
+      MockEasy;
+
+    sub new {
+        my ( $class, %opts ) = @_;
+        return bless \%opts, $class;
+    }
+
+    sub getinfo {
+        my ( $self, $key ) = @_;
+
+        # Only two keys are used: RESPONSE_CODE and EFFECTIVE_URL.
+        # We distinguish them by value rather than importing constants.
+        return $self->{response_code} if $key == 0x00200002;    # CURLINFO_RESPONSE_CODE
+        return $self->{effective_url} if $key == 0x00100001;    # CURLINFO_EFFECTIVE_URL
+        die "MockEasy::getinfo: unknown key $key";
+    }
+}
+
+# --- happy path: valid status line ----------------------------------------
+
+{
+    my $easy = MockEasy->new(
+        response_code => 200,
+        effective_url => 'https://example.com/acme',
+    );
+
+    my $head = "HTTP/1.1 200 OK\r\ncontent-type: application/json\r\n";
+    my $body = '{"status":"valid"}';
+
+    my $resp = Net::ACME2::Curl::_imitate_http_tiny( $easy, $head, $body );
+
+    is $resp->{status},  200,   'status from valid response';
+    is $resp->{reason},  'OK',  'reason parsed from status line';
+    is $resp->{content}, $body, 'body passed through';
+    is $resp->{headers}{'content-type'}, 'application/json', 'header parsed';
+}
+
+# --- unparseable status line: must throw, not silently continue ------------
+
+sub test_unparseable_status_line_throws {
+    my $easy = MockEasy->new(
+        response_code => 200,
+        effective_url => 'https://example.com/acme',
+    );
+
+    # A garbage first line that does not match "PROTO STATUS REASON".
+    my $head = "GARBAGE\r\ncontent-type: text/plain\r\n";
+    my $body = 'irrelevant';
+
+    # Before the fix this would only warn and return a response with an
+    # empty reason — silently corrupting the parsed result.  After the fix
+    # it must die with a structured exception.
+    throws_ok {
+        Net::ACME2::Curl::_imitate_http_tiny( $easy, $head, $body );
+    }
+    qr/[Uu]nparsable.*header/i,
+        'unparseable status line throws instead of warning';
+}
+
+test_unparseable_status_line_throws();
+
+# --- empty header block: reason stays undef / does not crash ---------------
+
+{
+    my $easy = MockEasy->new(
+        response_code => 0,
+        effective_url => 'https://example.com/acme',
+    );
+
+    # Completely empty header — split produces no lines.
+    my $resp = Net::ACME2::Curl::_imitate_http_tiny( $easy, q<>, 'body' );
+
+    is $resp->{reason}, undef, 'empty header yields undef reason (no crash)';
+}
+
+done_testing();