diff --git a/easybuild/easyconfigs/c/casacore/casacore-3.4.0-foss-2021b.eb b/easybuild/easyconfigs/c/casacore/casacore-3.4.0-foss-2021b.eb
index aab5e755fdf..ad0813959d7 100644
--- a/easybuild/easyconfigs/c/casacore/casacore-3.4.0-foss-2021b.eb
+++ b/easybuild/easyconfigs/c/casacore/casacore-3.4.0-foss-2021b.eb
@@ -31,6 +31,7 @@ dependencies = [
     ('CFITSIO', '3.49'),
     ('WCSLIB', '7.11'),
     ('HDF5', '1.12.1'),
+    ('GSL', '2.7'),
     ('SciPy-bundle', '2021.10'),
     ('Boost.Python', '1.77.0'),
     ('ncurses', '6.2'),