diff --git a/README.md b/README.md
index d1330b8..101220e 100644
--- a/README.md
+++ b/README.md
@@ -84,11 +84,11 @@ Note that for Calabi–Yau dimensions larger than four, the additional
 
 ## Operators and periods
 
-`operators.sage` and `period.sage` provide classes for working with Picard–Fuchs operators and their
+`operators.sage` and `periods.sage` provide classes for working with Picard–Fuchs operators and their
 period solutions: `PFOperator`, `PFIdeal` and `Period`, together with Ansatz variants of the first and
 last (`PFOperatorAnsatz`, `PeriodAnsatz`) used to search for unknown operators or periods of a given
-z- and theta-degree. The operator classes live in `operators.sage`, the period classes in `period.sage`;
-since the two depend on each other, load `period.sage`, which also loads `operators.sage`.
+z- and theta-degree. The operator classes live in `operators.sage`, the period classes in `periods.sage`;
+since the two depend on each other, load `periods.sage`, which also loads `operators.sage`.
 
 A `PFOperator` is parsed from a string in the variables `z0, ..., z<n-1>` and `theta0, ..., theta<n-1>`,
 the logarithmic derivatives theta_i = z_i d/dz_i. For example, the quintic's Picard&ndash;Fuchs operator:
diff --git a/tests/test_period_computation.py b/tests/test_period_computation.py
index 1aac36e..8df924c 100644
--- a/tests/test_period_computation.py
+++ b/tests/test_period_computation.py
@@ -2,7 +2,7 @@ import os
 
 from sage.all import *  # noqa: F401
 
-load(os.path.join(os.path.dirname(__file__), "..", "sage", "period.sage"))
+load(os.path.join(os.path.dirname(__file__), "..", "sage", "periods.sage"))
 
 
 def test_find_power_series_solution_recovers_quintic_period():