diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 172376e4c..86ae739ae 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -81,16 +81,21 @@ jobs:
               set -ex
 
               yum install -y tcl-devel zlib-devel libffi-devel \
-                devtoolset-11 flex gperf patchelf \
+                devtoolset-11 gperf patchelf \
                 elfutils-devel elfutils-libelf-devel libdwarf-devel
 
               source /opt/rh/devtoolset-11/enable
 
-              # Build bison >= 3.x from source
+              # Build bison >= 3.x from source (CentOS 7 ships an old version)
               curl -L https://ftp.gnu.org/gnu/bison/bison-3.8.2.tar.gz | tar -xzC /tmp
               cd /tmp/bison-3.8.2 && ./configure && make -j$(nproc) && make install
               cd /src
 
+              # Build flex >= 2.6 from source (CentOS 7 ships 2.5.37, Yosys needs >= 2.6)
+              curl -L https://github.com/westes/flex/releases/download/v2.6.4/flex-2.6.4.tar.gz | tar -xzC /tmp
+              cd /tmp/flex-2.6.4 && ./configure && make -j$(nproc) && make install
+              cd /src
+
               # Use the manylinux2014 Python 3.13
               export PATH=/opt/python/cp313-cp313/bin:$PATH