diff --git a/python-string_utils.spec b/python-string_utils.spec
index 1741112..5eddd06 100644
--- a/python-string_utils.spec
+++ b/python-string_utils.spec
@@ -47,6 +47,7 @@ BuildRequires: python%{python3_pkgversion}-setuptools
 %else
 BuildRequires: python3-devel
 BuildRequires: python3-setuptools
+BuildRequires: python3-sphinx_rtd_theme
 %endif
 BuildRequires: git