diff --git a/BUILD.boost b/BUILD.boost
index a008279f3..3a920d794 100644
--- a/BUILD.boost
+++ b/BUILD.boost
@@ -145,8 +145,8 @@ boost_library(
         "libs/context/src/untested.cpp",
         "libs/context/src/continuation.cpp",
     ],
-    copts = select({
-        ":windows_x86_64": ["/DBOOST_CONTEXT_EXPORT="],
+    defines = select({
+        ":windows_x86_64": ["BOOST_CONTEXT_EXPORT"],
         "//conditions:default": [],
     }),
     visibility = ["//visibility:public"],
@@ -187,9 +187,9 @@ boost_library(
         "libs/fiber/examples/asio/round_robin.hpp",
         "libs/fiber/examples/asio/yield.hpp",
     ],
-    copts = select({
+    defines = select({
         ":windows_x86_64": [
-            "/D_WIN32_WINNT=0x0601",
+            "_WIN32_WINNT=0x0601",
         ],
         "//conditions:default": [],
     }),
@@ -329,7 +329,15 @@ boost_library(
         ],
         "//conditions:default": [],
     }),
-    linkopts = ["-lpthread"],
+    linkopts = select({
+        ":linux": [
+            "-lpthread",
+        ],
+        ":osx_x86_64": [
+            "-lpthread",
+        ],
+        "//conditions:default": [],
+    }),
     deps = [
         ":bind",
         ":date_time",
@@ -1903,6 +1911,12 @@ boost_library(
         ":tti",
         ":type_traits",
     ],
+    linkopts = select({
+        ":windows": [
+            "bcrypt.lib"
+        ],
+        "//conditions:default": [],
+    }),
 )
 
 boost_library(
diff --git a/boost/boost.bzl b/boost/boost.bzl
index fd052fa16..5898fdb0a 100644
--- a/boost/boost.bzl
+++ b/boost/boost.bzl
@@ -25,7 +25,7 @@ default_copts = select({
     "//conditions:default": [],
 })
 
-default_defines = select({
+default_defines = ["BOOST_USE_VALGRIND"] + select({
     ":windows_x86_64": ["BOOST_ALL_NO_LIB"],  # Turn auto_link off in MSVC compiler
     "//conditions:default": [],
 })