diff --git a/sr.c b/sr.c
index 7a36451e..c48c05f2 100644
--- a/sr.c
+++ b/sr.c
@@ -574,7 +574,15 @@ static int ckpt_file_crc( const char* path, U64* size, U32* crc, int dosync )
     ssize_t n;
     U32     c = crc32( 0L, Z_NULL, 0 );
     U64     s = 0;
-    int     fd = HOPEN( path, O_RDONLY | O_BINARY );
+    /* O_RDWR, not O_RDONLY. In the browser build                      */
+    /* WasmFS reads an OPFS file opened read-only through a Blob, and   */
+    /* each read() makes a new JS ArrayBuffer of its size (64 KB here)  */
+    /* in the OPFS proxy thread: about 2.1 MB of garbage per checkpoint */
+    /* that only that worker GC frees (Chromium: the renderer grew      */
+    /* 1.8 MiB per checkpoint between GCs, +120-150 MiB/h in the 60-min */
+    /* soak). A read-write open uses a sync access handle that reads    */
+    /* into wasm memory. Nothing is written; native: the same reads.    */
+    int     fd = HOPEN( path, O_RDWR | O_BINARY );
     if (fd < 0)
         return -1;
     while ((n = read( fd, buf, sizeof( buf ))) > 0)