diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index 407c548..5b952d4 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -2908,6 +2908,17 @@ ProcessInterrupts(void)
 			DisableNotifyInterrupt();
 			DisableCatchupInterrupt();
 			pgstat_report_recovery_conflict(RecoveryConflictReason);
+
+			/*
+			 * We can't use ereport(ERROR) here, because any longjmps
+			 * in DoingCommandRead state run the risk of violating our
+			 * protocol or the SSL protocol, by interrupting OpenSSL in
+			 * the middle of changing its internal state.
+			 *
+			 * Currently, the only option is to promote ERROR to FATAL
+			 * until we figure out a better way to handle errors in this
+			 * state.
+			 */
 			if (DoingCommandRead)
 				ereport(FATAL,
 						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),