diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index e7c8e67c..287d42fb 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -11,67 +11,67 @@ jobs:
       matrix:
         include:
           - python-version: "3.7"
-            sundials-version: "6.1.0"
+            sundials-version: "6.5.0"
             tox-env: py37
             sundials-precision: double
             sundials-index-size: 64
           - python-version: "3.8"
-            sundials-version: "6.1.0"
+            sundials-version: "6.5.0"
             tox-env: py38
             sundials-precision: double
             sundials-index-size: 64
           - python-version: "3.9"
-            sundials-version: "6.1.0"
+            sundials-version: "6.5.0"
             tox-env: py39
             sundials-precision: double
             sundials-index-size: 64
           - python-version: "3.10"
-            sundials-version: "6.1.0"
+            sundials-version: "6.5.0"
             tox-env: py310
             sundials-precision: double
             sundials-index-size: 64
           - python-version: "3.11"
-            sundials-version: "6.1.0"
+            sundials-version: "6.5.0"
             tox-env: py311
             sundials-precision: double
             sundials-index-size: 64
           - python-version: "3.12"
-            sundials-version: "6.1.0"
+            sundials-version: "6.5.0"
             tox-env: py312
             sundials-precision: double
             sundials-index-size: 64
           - python-version: "3.11"
-            sundials-version: "6.1.0"
+            sundials-version: "6.5.0"
             tox-env: doctr
             sundials-precision: double
             sundials-index-size: 64
           - python-version: "3.11"
-            sundials-version: "6.1.0"
+            sundials-version: "6.5.0"
             tox-env: docs
             sundials-precision: double
             sundials-index-size: 64
           - python-version: "3.11"
-            sundials-version: "6.1.0"
+            sundials-version: "6.5.0"
             tox-env: check-manifest
             sundials-precision: double
             sundials-index-size: 64
           - python-version: "3.11"
-            sundials-version: "6.1.0"
+            sundials-version: "6.5.0"
             tox-env: checkreadme
             sundials-precision: double
             sundials-index-size: 64
           - python-version: "3.11"
-            sundials-version: "6.1.0"
+            sundials-version: "6.5.0"
             tox-env: py311
             sundials-precision: double
             sundials-index-size: 32
           - python-version: "3.11"
-            sundials-version: "6.1.0"
+            sundials-version: "6.5.0"
             tox-env: py311
             sundials-precision: single
             sundials-index-size: 64
           - python-version: "3.11"
-            sundials-version: "6.1.0"
+            sundials-version: "6.5.0"
             tox-env: py311
             sundials-precision: extended
             sundials-index-size: 64