diff --git a/src/liblzma/api/lzma/container.h b/src/liblzma/api/lzma/container.h
index 52667b6..34cf6f4 100644
--- a/src/liblzma/api/lzma/container.h
+++ b/src/liblzma/api/lzma/container.h
@@ -60,7 +60,6 @@
 #define LZMA_PRESET_EXTREME       (UINT32_C(1) << 31)
 
 
-#ifdef LZMA_UNSTABLE /* Unstable API that may change. Use only for testing. */
 /**
  * \brief       Multithreading options
  */
@@ -180,7 +179,6 @@
 	void *reserved_ptr4;
 
 } lzma_mt;
-#endif
 
 
 /**
@@ -314,7 +312,6 @@
 		lzma_nothrow lzma_attr_warn_unused_result;
 
 
-#ifdef LZMA_UNSTABLE /* Unstable API that may change. Use only for testing. */
 /**
  * \brief       Calculate approximate memory usage of multithreaded .xz encoder
  *
@@ -356,7 +353,6 @@
 extern LZMA_API(lzma_ret) lzma_stream_encoder_mt(
 		lzma_stream *strm, const lzma_mt *options)
 		lzma_nothrow lzma_attr_warn_unused_result;
-#endif
 
 
 /**
diff --git a/src/liblzma/common/common.h b/src/liblzma/common/common.h
index af14e47..955d784 100644
--- a/src/liblzma/common/common.h
+++ b/src/liblzma/common/common.h
@@ -32,8 +32,6 @@
 
 #define LZMA_API(type) LZMA_API_EXPORT type LZMA_API_CALL
 
-#define LZMA_UNSTABLE
-
 #include "lzma.h"
 
 // These allow helping the compiler in some often-executed branches, whose
diff --git a/src/xz/private.h b/src/xz/private.h
index 9576da8..4acfa8d 100644
--- a/src/xz/private.h
+++ b/src/xz/private.h
@@ -13,7 +13,6 @@
 #include "sysdefs.h"
 #include "mythread.h"
 
-#define LZMA_UNSTABLE
 #include "lzma.h"
 
 #include <sys/types.h>