diff --git a/tests/unit/test_optimisation.py b/tests/unit/test_optimisation.py
index b0fd2ae0..b1ed740a 100644
--- a/tests/unit/test_optimisation.py
+++ b/tests/unit/test_optimisation.py
@@ -40,7 +40,7 @@ def two_parameters(self):
         return pybop.Parameters(
             pybop.Parameter(
                 "Negative electrode active material volume fraction",
-                prior=pybop.Gaussian(0.6, 0.02),
+                prior=pybop.Gaussian(0.6, 0.2),
                 bounds=[0.58, 0.62],
             ),
             pybop.Parameter(