diff -r 66afe8954ff9 -r c190ce0aab98 src/server/safs/proxy.c
--- a/src/server/safs/proxy.c	Sat Mar 14 12:42:48 2026 +0100
+++ b/src/server/safs/proxy.c	Sat Mar 14 12:49:53 2026 +0100
@@ -242,6 +242,9 @@
                 log_ereport(LOG_FAILURE, "proxy_response_write: cannot add write poll");
             }
             return HTTP_CLIENT_CALLBACK_WOULD_BLOCK;
+        } else {
+            log_ereport(LOG_FAILURE, "proxy_response_write failed: %s", strerror(st->io_errno));
+            return HTTP_CLIENT_CALLBACK_ERROR;
         }
     }
     return ret;