diff --git a/lrzip_private.h b/lrzip_private.h
index 1744ecc..f8a7dde 100644
--- a/lrzip_private.h
+++ b/lrzip_private.h
@@ -377,6 +377,7 @@ struct rzip_control {
 	pthread_mutex_t control_lock;
 	unsigned char eof;
 	unsigned char magic_written;
+	bool lzma_prop_set;
 
 	pthread_mutex_t cksumlock;
 	md5_ctx ctx;
diff --git a/stream.c b/stream.c
index a77a9e1..0431d52 100644
--- a/stream.c
+++ b/stream.c
@@ -304,6 +304,7 @@ static int gzip_compress_buf(rzip_control *control, struct compress_thread *cthr
 
 static int lzma_compress_buf(rzip_control *control, struct compress_thread *cthread)
 {
+	unsigned char lzma_properties[5]; /* lzma properties, encoded */
 	int lzma_level, lzma_ret;
 	size_t prop_size = 5; /* return value for lzma_properties */
 	uchar *c_buf;
@@ -325,10 +326,10 @@ retry:
 	}
 
 	/* with LZMA SDK 4.63, we pass compression level and threads only
-	 * and receive properties in control->lzma_properties */
+	 * and receive properties in lzma_properties */
 
 	lzma_ret = LzmaCompress(c_buf, &dlen, cthread->s_buf,
-		(size_t)cthread->s_len, control->lzma_properties, &prop_size,
+		(size_t)cthread->s_len, lzma_properties, &prop_size,
 				lzma_level,
 				0, /* dict size. set default, choose by level */
 				-1, -1, -1, -1, /* lc, lp, pb, fb */
@@ -375,6 +376,14 @@ retry:
 		return 0;
 	}
 
+	/* Make sure multiple threads don't race on writing lzma_properties */
+	lock_mutex(control, &control->control_lock);
+	if (!control->lzma_prop_set) {
+		memcpy(control->lzma_properties, lzma_properties, 5);
+		control->lzma_prop_set = true;
+	}
+	unlock_mutex(control, &control->control_lock);
+
 	cthread->c_len = dlen;
 	free(cthread->s_buf);
 	cthread->s_buf = c_buf;