diff --git a/contrib/pg_upgrade/controldata.c b/contrib/pg_upgrade/controldata.c
index 78d62c76f4d0262361ae0d44de203e72dc9acc85..0011c20bf1febfdffc5ab9cc59f824751a88d99f 100644
--- a/contrib/pg_upgrade/controldata.c
+++ b/contrib/pg_upgrade/controldata.c
@@ -88,7 +88,7 @@ get_control_data(migratorContext *ctx, ClusterInfo *cluster, bool live_check)
 	while (fgets(bufin, sizeof(bufin), output))
 	{
 		if (ctx->debug)
-			fprintf(ctx->debug_fd, bufin);
+			fputs(bufin, ctx->debug_fd);
 
 #ifdef WIN32
 		/*