diff --git a/python-biopython.spec b/python-biopython.spec
index 219aa45..ef71202 100644
--- a/python-biopython.spec
+++ b/python-biopython.spec
@@ -50,7 +50,7 @@ Summary:  Python tools for computational molecular biology
 
 # Build required packages
 BuildRequires:    python2-devel
-BuildRequires:    flex-devel
+#BuildRequires:    flex-devel
 BuildRequires:    %{py2_prefix}-reportlab
 BuildRequires:    %{py2_prefix}-psycopg2
 BuildRequires:    %{py2_prefix}-rdflib
@@ -69,7 +69,8 @@ BuildRequires:    %{py2_prefix}-mysql-connector
 Requires:         %{py2_prefix}-networkx
 Requires:         %{py2_prefix}-reportlab
 Requires:         %{py2_prefix}-psycopg2
-Requires:         wise2
+Requires:         wise2%{?_isa}
+Requires:         flex%{?_isa}
 Requires:         %{py2_prefix}-rdflib
 %if 0%{?rhel}
 Requires:         MySQL-%{py2_prefix}
@@ -96,7 +97,7 @@ Summary: Python3 tools for computational molecular biology
 
 BuildRequires:    python%{python3_pkgversion}-devel
 BuildRequires:    python%{python3_pkgversion}-setuptools
-BuildRequires:    flex-devel
+#BuildRequires:    flex-devel
 BuildRequires:    python%{python3_pkgversion}-reportlab
 BuildRequires:    python%{python3_pkgversion}-numpy
 BuildRequires:    python%{python3_pkgversion}-mysql
@@ -110,7 +111,8 @@ Requires:         python%{python3_pkgversion}-reportlab
 Requires:         python%{python3_pkgversion}-numpy
 Requires:         python%{python3_pkgversion}-mysql
 Requires:         python%{python3_pkgversion}-psycopg2
-Requires:         wise2
+Requires:         wise2%{?_isa}
+Requires:         flex%{?_isa}
 Requires:         python%{python3_pkgversion}-rdflib
 
 %description -n python%{python3_pkgversion}-%{module}
@@ -125,7 +127,7 @@ Summary: Python3 tools for computational molecular biology
 %{?python_provide:%python_provide python%{python3_other_pkgversion}-%{module}}
 
 BuildRequires:    python%{python3_other_pkgversion}-devel
-BuildRequires:    flex-devel
+#BuildRequires:    flex-devel
 BuildRequires:    python%{python3_other_pkgversion}-reportlab
 BuildRequires:    python%{python3_other_pkgversion}-numpy
 BuildRequires:    python%{python3_other_pkgversion}-mysql
@@ -139,7 +141,8 @@ Requires:         python%{python3_other_pkgversion}-reportlab
 Requires:         python%{python3_other_pkgversion}-numpy
 Requires:         python%{python3_other_pkgversion}-mysql
 Requires:         python%{python3_other_pkgversion}-psycopg2
-Requires:         wise2
+Requires:         wise2%{?_isa}
+Requires:         flex%{?_isa}
 Requires:         python%{python3_other_pkgversion}-rdflib
 
 %description -n python%{python3_other_pkgversion}-%{module}
@@ -314,8 +317,9 @@ popd
 %license %{module}-%{version}/LICENSE.rst
 
 %changelog
-* Tue Jul 28 2020 Fedora Release Engineering <releng@fedoraproject.org> - 1.77-4
+* Tue Jul 28 2020 Antonio Trande <sagitter@fedoraproject.org> - 1.77-4
 - Rebuilt for https://fedoraproject.org/wiki/Fedora_33_Mass_Rebuild
+- Remove flex as BR dependency
 
 * Wed Jun 24 2020 Antonio Trande <sagitter@fedoraproject.org> - 1.77-3
 - BuildRequires python3-setuptools explicitly