diff --git a/.github/workflows/horizon.yml b/.github/workflows/horizon.yml
index 0dce67c722..1b51ee4d55 100644
--- a/.github/workflows/horizon.yml
+++ b/.github/workflows/horizon.yml
@@ -34,7 +34,7 @@ jobs:
       HORIZON_INTEGRATION_TESTS_CORE_MAX_SUPPORTED_PROTOCOL: ${{ matrix.protocol-version }}
       HORIZON_INTEGRATION_TESTS_CAPTIVE_CORE_USE_DB: true
       PROTOCOL_21_CORE_DEBIAN_PKG_VERSION: 21.3.1-2006.4ede19620.focal
-      PROTOCOL_21_CORE_DOCKER_IMG: stellar/stellar-core:21
+      PROTOCOL_21_CORE_DOCKER_IMG: stellar/stellar-core:21.3.1-2006.4ede19620.focal
       PROTOCOL_21_SOROBAN_RPC_DOCKER_IMG: stellar/soroban-rpc:21.0.0-rc2-73
       PGHOST: localhost
       PGPORT: 5432