diff --git a/pkgs/development/python-modules/ecdsa/default.nix b/pkgs/development/python-modules/ecdsa/default.nix
index dd17b454ba69..cf8c64fb787d 100644
--- a/pkgs/development/python-modules/ecdsa/default.nix
+++ b/pkgs/development/python-modules/ecdsa/default.nix
@@ -34,6 +34,13 @@ buildPythonPackage (finalAttrs: {
     pytestCheckHook
   ];
 
+  patches = [
+    # Python update caused one of the tests to fail. A patch that fixes this
+    # has been submitted upstream, yet to be applied.
+    # https://github.com/tlsfuzzer/python-ecdsa/pull/371
+    ./pr-371-fix-test-2026-05-23.patch
+  ];
+
   passthru.updateScript = gitUpdater {
     rev-prefix = "python-ecdsa-";
   };
diff --git a/pkgs/development/python-modules/ecdsa/pr-371-fix-test-2026-05-23.patch b/pkgs/development/python-modules/ecdsa/pr-371-fix-test-2026-05-23.patch
new file mode 100644
index 000000000000..90d25d7db525
--- /dev/null
+++ b/pkgs/development/python-modules/ecdsa/pr-371-fix-test-2026-05-23.patch
@@ -0,0 +1,30 @@
+From f8e0f3a0035b44fa2541e2c447ed1599f220c4b5 Mon Sep 17 00:00:00 2001
+From: Alexander Shadchin <shadchin@yandex-team.com>
+Date: Thu, 9 Apr 2026 12:22:29 +0300
+Subject: [PATCH] Fix tests with new Python
+
+---
+ src/ecdsa/der.py | 9 ++++-----
+ 1 file changed, 4 insertions(+), 5 deletions(-)
+
+diff --git a/src/ecdsa/der.py b/src/ecdsa/der.py
+index 5d35d698..587d7852 100644
+--- a/src/ecdsa/der.py
++++ b/src/ecdsa/der.py
+@@ -464,12 +464,11 @@ def unpem(pem):
+     if isinstance(pem, text_type):  # pragma: no branch
+         pem = pem.encode()
+ 
++    lines = (l.strip() for l in pem.split(b"\n"))
+     d = b"".join(
+-        [
+-            l.strip()
+-            for l in pem.split(b"\n")
+-            if l and not l.startswith(b"-----")
+-        ]
++        l
++        for l in lines
++        if l and not l.startswith(b"-----")
+     )
+     return base64.b64decode(d)
+