diff --git a/docker/fedora/prepare.sh b/docker/fedora/prepare.sh
index 61f15ca7e5..76e9ff3c48 100644
--- a/docker/fedora/prepare.sh
+++ b/docker/fedora/prepare.sh
@@ -42,6 +42,7 @@ dnf install -y \
     ffmpeg \
     ffmpeg-libs \
     ffmpeg-devel \
+    flex \
     flite \
     flite-devel \
     mono-devel \