diff --git a/java-spanner/google-cloud-spanner/src/main/java/com/google/cloud/spanner/connection/AbstractBaseUnitOfWork.java b/java-spanner/google-cloud-spanner/src/main/java/com/google/cloud/spanner/connection/AbstractBaseUnitOfWork.java
index 1d71e062cbb4..a92d696665d2 100644
--- a/java-spanner/google-cloud-spanner/src/main/java/com/google/cloud/spanner/connection/AbstractBaseUnitOfWork.java
+++ b/java-spanner/google-cloud-spanner/src/main/java/com/google/cloud/spanner/connection/AbstractBaseUnitOfWork.java
@@ -388,7 +388,11 @@ public <ReqT, RespT> ApiCallContext configure(
                     if (remainingTimeout <= 0) {
                       remainingTimeout = 1;
                     }
-                    return GrpcCallContext.createDefault()
+                    // Build from the input context so existing call options
+                    // (e.g. grpc-gcp's AFFINITY_KEY set by GapicSpannerRpc.newCallContext)
+                    // survive the GrpcCallContext.merge() — merge rebuilds CallOptions from
+                    // the configurator result, dropping any options it does not carry.
+                    return ((GrpcCallContext) context)
                         .withTimeoutDuration(Duration.ofNanos(remainingTimeout));
                   }
                   return null;