diff --git a/.github/workflows/horizon.yml b/.github/workflows/horizon.yml
index 1a5415f74b..522d8f528e 100644
--- a/.github/workflows/horizon.yml
+++ b/.github/workflows/horizon.yml
@@ -89,6 +89,8 @@ jobs:
           sudo apt list --installed | grep libc++
           sudo apt-get remove -y libc++1-* libc++abi1-* || true
 
+          # debug https://apt.stellar.org/SDF.asc
+          curl -sL https://apt.stellar.org/SDF.asc
           sudo wget -qO - https://apt.stellar.org/SDF.asc | APT_KEY_DONT_WARN_ON_DANGEROUS_USAGE=true sudo apt-key add -
           sudo bash -c 'echo "deb https://apt.stellar.org focal unstable" > /etc/apt/sources.list.d/SDF-unstable.list'
           sudo apt-get update && sudo apt-get install -y stellar-core="$PROTOCOL_${{ matrix.protocol-version }}_CORE_DEBIAN_PKG_VERSION"