diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index e6c9e480d3..dc1f1df6dd 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -1288,7 +1288,7 @@ setup_config(void)
 	conflines = replace_token(conflines, "#dynamic_shared_memory_type = posix",
 							  repltok);
 
-#if !USE_PREFETCH
+#ifndef USE_PREFETCH
 	conflines = replace_token(conflines,
 							  "#effective_io_concurrency = 1",
 							  "#effective_io_concurrency = 0");