diff --git a/compress/function/zstd.c b/compress/function/zstd.c
index d5ba8cc..5614b9e 100644
--- a/compress/function/zstd.c
+++ b/compress/function/zstd.c
@@ -106,7 +106,8 @@ static enum b_status compress(struct b_compressor *compressor)
 
 	while (1) {
 		size_t in_available = 0, out_capacity = 0;
-		void *in_buf = NULL, *out_buf = NULL;
+		const void *in_buf = NULL;
+		void *out_buf = NULL;
 
 		status = b_ringbuffer_open_read_buffer(in, &in_buf, &in_available);
 		if (!B_OK(status)) {
@@ -221,7 +222,8 @@ static enum b_status decompress(struct b_compressor *compressor)
 
 	while (!(compressor->c_flags & COMPRESSOR_EOF)) {
 		size_t in_available = 0, out_capacity = 0;
-		void *in_buf = NULL, *out_buf = NULL;
+		const void *in_buf = NULL;
+		void *out_buf = NULL;
 
 		status = b_ringbuffer_open_read_buffer(in, &in_buf, &in_available);
 		if (!B_OK(status)) {
@@ -267,7 +269,7 @@ static enum b_status decompress(struct b_compressor *compressor)
 		b_ringbuffer_close_write_buffer(out, &out_buf, z_out.pos);
 	}
 
-	if ((status == B_ERR_NO_SPACE || status == B_ERR_NO_SPACE)
+	if ((status == B_ERR_NO_SPACE || status == B_ERR_NO_DATA)
 	    && nr_consumed > 0) {
 		status = B_SUCCESS;
 	}