diff --git a/.gitmodules b/.gitmodules
index 33f9f2d5..5eeef4d9 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -1,3 +1,8 @@
+[submodule "vendor/bzip2"]
+    path = vendor/bzip2
+    url = https://github.com/upx/upx-vendor-bzip2.git
+    branch = upx-vendor
+    shallow = true
 [submodule "vendor/doctest"]
     path = vendor/doctest
     url = https://github.com/upx/upx-vendor-doctest.git
@@ -23,3 +28,8 @@
     url = https://github.com/upx/upx-vendor-zlib.git
     branch = upx-vendor
     shallow = true
+[submodule "vendor/zstd"]
+    path = vendor/zstd
+    url = https://github.com/upx/upx-vendor-zstd.git
+    branch = upx-vendor
+    shallow = true
diff --git a/misc/make/Makefile-extra.mk b/misc/make/Makefile-extra.mk
index a7afd9f9..4f8a1cb3 100644
--- a/misc/make/Makefile-extra.mk
+++ b/misc/make/Makefile-extra.mk
@@ -375,7 +375,7 @@ UPX_CMAKE_CONFIG_FLAGS += $(call __add_cmake_config,UPX_CONFIG_EXTRA_COMPILE_OPT
 # check git submodules
 #***********************************************************************
 
-SUBMODULES = doctest lzma-sdk ucl valgrind zlib
+SUBMODULES = bzip2 doctest lzma-sdk ucl valgrind zlib zstd
 
 $(foreach 1,$(SUBMODULES),$(if $(wildcard vendor/$1/[CL]*),,\
   $(error ERROR: missing git submodule '$1'; run 'git submodule update --init')))
diff --git a/vendor/bzip2 b/vendor/bzip2
new file mode 160000
index 00000000..f6ff91c4
--- /dev/null
+++ b/vendor/bzip2
@@ -0,0 +1 @@
+Subproject commit f6ff91c4ab4998a87bd17251fa311d84ff0797bc
diff --git a/vendor/zstd b/vendor/zstd
new file mode 160000
index 00000000..e204efb9
--- /dev/null
+++ b/vendor/zstd
@@ -0,0 +1 @@
+Subproject commit e204efb9c2510b632152449fdc6512752d77e6b0