diff --git a/.gitignore b/.gitignore
index 682df9887..63a7c737c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -34,6 +34,7 @@ _build
 /infer/models/java/Makefile
 /infer/models/objc/Makefile
 /infer/src/Makefile
+/.buckversion
 
 # IntelliJ files
 /scripts/.idea/
diff --git a/Makefile.in b/Makefile.in
index f91db527e..9494cbff8 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -65,7 +65,7 @@ clang_setup:
 	$(FCP_DIR)/clang/setup.sh
 
 clang_plugin: clang_setup
-ifeq (@INFER_IS_RELEASE@,no)
+ifeq (@IS_RELEASE_TREE@,no)
 	$(MAKE) -C $(FCP_DIR)/libtooling all \
 	  CC=@CC@ CXX=@CXX@ \
 	  CXX="@CXX@" CXXFLAGS="@CXXFLAGS@" \
diff --git a/configure.ac b/configure.ac
index 2ebb41f86..e91ca9eb6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -28,13 +28,15 @@ AC_SUBST([INFER_MAJOR])
 AC_SUBST([INFER_MINOR])
 AC_SUBST([INFER_PATCH])
 
-# record if we are in a release of Infer
-AC_MSG_CHECKING([if we are in an Infer release build])
-is_infer_release=no
-AS_IF([test -f ".release"], [is_infer_release=yes])
-INFER_IS_RELEASE=$is_infer_release
-AC_SUBST([INFER_IS_RELEASE])
-AC_MSG_RESULT([$is_infer_release])
+# are we in a release source tree
+AC_CHECK_FILE([.release], [is_release_tree=yes], [is_release_tree=no])
+IS_RELEASE_TREE=$is_release_tree
+AC_SUBST([IS_RELEASE_TREE])
+
+# are we in an internal source tree
+AC_CHECK_FILE([.facebook], [is_facebook_tree=yes], [is_facebook_tree=no])
+IS_FACEBOOK_TREE=$is_facebook_tree
+AC_SUBST([IS_FACEBOOK_TREE])
 
 # to compile the facebook-clang-plugins
 AC_ARG_VAR([CLANG_PREFIX], [directory where clang is installed (defaults=$PWD/facebook-clang-plugins/clang)])
@@ -69,7 +71,7 @@ AC_ARG_WITH(fcp-clang,
   AS_HELP_STRING([--without-fcp-clang],
     [do not use $CLANG_PREFIX/bin/clang to override the default compiler (default is to override if in an infer release)]),
   ,
-  with_fcp_clang=$is_infer_release)
+  with_fcp_clang=$is_release_tree)
 
 AS_IF([test "x$enable_c_analyzers" = "xyes"], [
   AC_MSG_CHECKING([whether to use the compilers in $CLANG_PREFIX/bin])
@@ -226,6 +228,18 @@ ENABLE_OCAML_BINANNOT=$enable_ocaml_bin_annot
 AC_SUBST([ENABLE_OCAML_BINANNOT])
 
 
+# We use Buck to run the Infer tests
+AC_MSG_CHECKING([which version of Buck to use])
+buckversion_file=.buckversion
+oss_buck_version=a965937ccdadf8119a98ab766c3feb0708dc424e
+fb_buck_version=440619c312cf07951891083d8f02d05a713205b5
+AS_IF([test x"$is_facebook_tree" = x"yes"],
+  [buck_version=$fb_buck_version],
+  [buck_version=$oss_buck_version])
+echo $buck_version > "$buckversion_file"
+AC_MSG_RESULT([$buck_version])
+
+
 AC_CONFIG_FILES([
   Makefile.config
   Makefile
diff --git a/infer/src/Makefile.in b/infer/src/Makefile.in
index 5be83f6b6..ce2531c00 100644
--- a/infer/src/Makefile.in
+++ b/infer/src/Makefile.in
@@ -11,7 +11,7 @@ include $(ROOT_DIR)/Makefile.config
 INFER_MAJOR = @INFER_MAJOR@
 INFER_MINOR = @INFER_MINOR@
 INFER_PATCH = @INFER_PATCH@
-INFER_IS_RELEASE = @INFER_IS_RELEASE@
+IS_RELEASE_TREE = @IS_RELEASE_TREE@
 
 ATDGEN = @ATDGEN@
 
@@ -122,12 +122,10 @@ CHECKCOPYRIGHT_MAIN = $(SCRIPT_SOURCES)/checkCopyright
 
 #### End of declarations ####
 
-# Check whether .facebook file exists in a root directory.
-# Based on that determine which code should be loaded
-ifeq ($(wildcard $(ROOT_DIR)/.facebook),)
-	EXTRA_DEPS = opensource
+ifeq (@IS_FACEBOOK_TREE@,yes)
+EXTRA_DEPS = facebook
 else
-	EXTRA_DEPS = facebook
+EXTRA_DEPS = opensource
 endif
 
 DEPENDENCIES = IR backend checkers eradicate harness \
@@ -268,7 +266,7 @@ version: backend/version.ml.in Makefile
 	  -e 's|@INFER_MAJOR[@]|$(INFER_MAJOR)|g' \
 	  -e 's|@INFER_MINOR[@]|$(INFER_MINOR)|g' \
 	  -e 's|@INFER_PATCH[@]|$(INFER_PATCH)|g' \
-	  -e 's|@INFER_IS_RELEASE[@]|$(INFER_IS_RELEASE)|g' \
+	  -e 's|@IS_RELEASE_TREE[@]|$(IS_RELEASE_TREE)|g' \
 	  -e "s|@INFER_GIT_COMMIT[@]|$$INFER_GIT_COMMIT|g" \
 	  -e "s|@INFER_GIT_BRANCH[@]|$$INFER_GIT_BRANCH|g" \
 	  $< > "$$TMPFILE"; \
diff --git a/infer/src/backend/version.ml.in b/infer/src/backend/version.ml.in
index 5ed7588da..ceaa74066 100644
--- a/infer/src/backend/version.ml.in
+++ b/infer/src/backend/version.ml.in
@@ -14,7 +14,7 @@ let patch = @INFER_PATCH@
 
 let commit = "@INFER_GIT_COMMIT@"
 let branch = "@INFER_GIT_BRANCH@"
-let is_release = string_equal "@INFER_IS_RELEASE@" "yes"
+let is_release = string_equal "@IS_RELEASE_TREE@" "yes"
 let tag = Printf.sprintf "v%d.%d.%d" major minor patch
 
 let versionString =