diff --git a/gzwrite.c b/gzwrite.c
index eb8a0e5..3030d74 100644
--- a/gzwrite.c
+++ b/gzwrite.c
@@ -609,7 +609,7 @@
     strm = &(state->strm);
 
     /* check that we're writing and that there's no error */
-    if (state->mode != GZ_WRITE || state->err != Z_OK)
+    if (state->mode != GZ_WRITE || state->err != Z_OK || state->direct)
         return Z_STREAM_ERROR;
 
     /* if no change is requested, then do nothing */