diff --git a/.github/workflows/horizon.yml b/.github/workflows/horizon.yml
index 9a9b17910a..25236bf88b 100644
--- a/.github/workflows/horizon.yml
+++ b/.github/workflows/horizon.yml
@@ -15,7 +15,7 @@ jobs:
         go: [1.18.6, 1.19.4]
         pg: [9.6.5]
         ingestion-backend: [db, captive-core, captive-core-remote-storage]
-        protocol-version: [18, 19, 20]
+        protocol-version: [19, 20]
     runs-on: ${{ matrix.os }}
     services:
       postgres:
@@ -38,8 +38,6 @@ jobs:
       PROTOCOL_20_CORE_DOCKER_IMG: gkudra/stellar-core:19.8.1-1234.f94d66031.focal-soroban
       PROTOCOL_19_CORE_DEBIAN_PKG_VERSION: 19.5.0-1108.ca2fb0605.focal
       PROTOCOL_19_CORE_DOCKER_IMG: stellar/stellar-core:19.5.0-1108.ca2fb0605.focal
-      PROTOCOL_18_CORE_DEBIAN_PKG_VERSION: 19.5.0-1108.ca2fb0605.focal
-      PROTOCOL_18_CORE_DOCKER_IMG: stellar/stellar-core:19.5.0-1108.ca2fb0605.focal
       PGHOST: localhost
       PGPORT: 5432
       PGUSER: postgres
@@ -103,7 +101,7 @@ jobs:
       uses: actions/cache@v3
       with:
         path: ./empty
-        key: horizon-hash-${{ hashFiles('./horizon') }}-${{ hashFiles('./clients/horizonclient/**') }}-${{ hashFiles('./protocols/horizon/**') }}-${{ hashFiles('./txnbuild/**') }}-${{ hashFiles('./services/horizon/internal/integration/**') }}-${{ env.PROTOCOL_20_CORE_DOCKER_IMG }}-${{ env.PROTOCOL_19_CORE_DOCKER_IMG }}-${{ env.PROTOCOL_18_CORE_DOCKER_IMG }}-${{ matrix.protocol-version }}
+        key: horizon-hash-${{ hashFiles('./horizon') }}-${{ hashFiles('./clients/horizonclient/**') }}-${{ hashFiles('./protocols/horizon/**') }}-${{ hashFiles('./txnbuild/**') }}-${{ hashFiles('./services/horizon/internal/integration/**') }}-${{ env.PROTOCOL_20_CORE_DOCKER_IMG }}-${{ env.PROTOCOL_19_CORE_DOCKER_IMG }}-${{ matrix.protocol-version }}
 
     - if: ${{ steps.horizon_binary_tests_hash.outputs.cache-hit != 'true' }}
       run: go test -race -timeout 35m -v ./services/horizon/internal/integration/...