diff --git a/buf/buf0flu.c b/buf/buf0flu.c
index f866fd105e2..b0fb46c8912 100644
--- a/buf/buf0flu.c
+++ b/buf/buf0flu.c
@@ -502,7 +502,7 @@ buf_flush_init_for_writing(
 						+ (PAGE_HEADER + PAGE_LEVEL)),
 				(ulong) page_zip->m_start,
 				(ulong) 2
-				* page_dir_get_n_heap(page_zip->data));
+				* (page_dir_get_n_heap(page_zip->data) - 2));
 
 			page_zip->data = NULL;
 		}
diff --git a/page/page0zip.c b/page/page0zip.c
index 8e160bd09b6..c917f3d8820 100644
--- a/page/page0zip.c
+++ b/page/page0zip.c
@@ -682,8 +682,10 @@ first_inflate:
 	ut_a(d_stream.avail_out < UNIV_PAGE_SIZE
 				- PAGE_ZIP_START - PAGE_DIR);
 
-	/* set heap_no and the status bits */
-	mach_write_to_2(dst - REC_NEW_HEAP_NO, heap_status);
+	if (UNIV_LIKELY(d_stream.avail_out != 0)) {
+		/* set heap_no and the status bits */
+		mach_write_to_2(dst - REC_NEW_HEAP_NO, heap_status);
+	}
 
 	err = inflate(&d_stream, Z_FINISH);