diff --git a/.github/workflows/horizon.yml b/.github/workflows/horizon.yml
index 8f38f7fe03..a9a084f501 100644
--- a/.github/workflows/horizon.yml
+++ b/.github/workflows/horizon.yml
@@ -15,7 +15,7 @@ jobs:
         go: [1.19.6, 1.20.1]
         pg: [9.6.5]
         ingestion-backend: [db, captive-core, captive-core-remote-storage]
-        protocol-version: [18, 19]
+        protocol-version: [19]
     runs-on: ${{ matrix.os }}
     services:
       postgres:
@@ -36,8 +36,6 @@ jobs:
       HORIZON_INTEGRATION_TESTS_CORE_MAX_SUPPORTED_PROTOCOL: ${{ matrix.protocol-version }}
       PROTOCOL_19_CORE_DEBIAN_PKG_VERSION: 19.8.0-1227.040a29c51.focal
       PROTOCOL_19_CORE_DOCKER_IMG: stellar/stellar-core:19.8.0-1227.040a29c51.focal
-      PROTOCOL_18_CORE_DEBIAN_PKG_VERSION: 19.8.0-1227.040a29c51.focal
-      PROTOCOL_18_CORE_DOCKER_IMG: stellar/stellar-core:19.8.0-1227.040a29c51.focal
       PGHOST: localhost
       PGPORT: 5432
       PGUSER: postgres
@@ -79,7 +77,7 @@ jobs:
         # libc++1-8 won't be installed if another version is installed (but apt won't give you a helpul
         # message about why the installation fails)
         sudo apt-get remove -y libc++1-10 libc++abi1-10 || true
-        
+
         sudo wget -qO - https://apt.stellar.org/SDF.asc | APT_KEY_DONT_WARN_ON_DANGEROUS_USAGE=true sudo apt-key add -
         sudo bash -c 'echo "deb https://apt.stellar.org focal unstable" > /etc/apt/sources.list.d/SDF-unstable.list'
         sudo apt-get update && sudo apt-get install -y stellar-core="$PROTOCOL_${{ matrix.protocol-version }}_CORE_DEBIAN_PKG_VERSION"
@@ -101,7 +99,7 @@ jobs:
       uses: actions/cache@v3
       with:
         path: ./empty
-        key: horizon-hash-${{ hashFiles('./horizon') }}-${{ hashFiles('./clients/horizonclient/**') }}-${{ hashFiles('./protocols/horizon/**') }}-${{ hashFiles('./txnbuild/**') }}-${{ hashFiles('./services/horizon/internal/integration/**') }}-${{ env.PROTOCOL_19_CORE_DOCKER_IMG }}-${{ env.PROTOCOL_18_CORE_DOCKER_IMG }}
+        key: horizon-hash-${{ hashFiles('./horizon') }}-${{ hashFiles('./clients/horizonclient/**') }}-${{ hashFiles('./protocols/horizon/**') }}-${{ hashFiles('./txnbuild/**') }}-${{ hashFiles('./services/horizon/internal/integration/**') }}-${{ env.PROTOCOL_19_CORE_DOCKER_IMG }}
 
     - if: ${{ steps.horizon_binary_tests_hash.outputs.cache-hit != 'true' }}
       run: go test -race -timeout 35m -v ./services/horizon/internal/integration/...