diff -up zstandard-0.16.0/c-ext/python-zstandard.h.orig zstandard-0.16.0/c-ext/python-zstandard.h
--- zstandard-0.16.0/c-ext/python-zstandard.h.orig	2021-10-16 23:41:56.000000000 +0200
+++ zstandard-0.16.0/c-ext/python-zstandard.h	2021-10-18 12:54:19.526520178 +0200
@@ -126,7 +126,7 @@ typedef struct {
     size_t outSize;
     int entered;
     int closing;
-    int closed;
+    char closed;
     int writeReturnRead;
     int closefd;
     unsigned long long bytesCompressed;
@@ -163,7 +163,7 @@ typedef struct {
     int closefd;
 
     int entered;
-    int closed;
+    char closed;
     unsigned long long bytesCompressed;
 
     ZSTD_inBuffer input;
@@ -243,7 +243,7 @@ typedef struct {
     /* Whether the context manager is active. */
     int entered;
     /* Whether we've closed the stream. */
-    int closed;
+    char closed;
 
     /* Number of bytes decompressed and returned to user. */
     unsigned long long bytesDecompressed;
@@ -270,7 +270,7 @@ typedef struct {
     size_t outSize;
     int entered;
     int closing;
-    int closed;
+    char closed;
     int writeReturnRead;
     int closefd;
 } ZstdDecompressionWriter;