diff --git a/src/include/openssl/base.h b/src/include/openssl/base.h
index 7a3adfb..88012ad 100644
--- a/src/include/openssl/base.h
+++ b/src/include/openssl/base.h
@@ -94,6 +94,8 @@ extern "C" {
 #define OPENSSL_PNACL
 #elif defined(__myriad2__)
 #define OPENSSL_32_BIT
+#elif defined(__s390x__)
+#define OPENSSL_64_BIT
 #else
 #error "Unknown target CPU"
 #endif
diff --git a/BUILD b/BUILD
index 6b645e61..c90b7beb 100644
--- a/BUILD
+++ b/BUILD
@@ -40,29 +40,46 @@ config_setting(
     values = {"cpu": "darwin"},
 )
 
-boringssl_copts = [
-    # Assembler option --noexecstack adds .note.GNU-stack to each object to
-    # ensure that binaries can be built with non-executable stack.
-    "-Wa,--noexecstack",
-
-    # This is needed on Linux systems (at least) to get rwlock in pthread.
-    "-D_XOPEN_SOURCE=700",
-
-    # This list of warnings should match those in the top-level CMakeLists.txt.
-    "-Wall",
-    "-Werror",
-    "-Wformat=2",
-    "-Wsign-compare",
-    "-Wmissing-field-initializers",
-    "-Wwrite-strings",
-    "-Wshadow",
-    "-fno-common",
-
-    # Modern build environments should be able to set this to use atomic
-    # operations for reference counting rather than locks. However, it's
-    # known not to work on some Android builds.
-    # "-DOPENSSL_C11_ATOMIC",
-] + select({
+config_setting(
+    name = "windows",
+    values = {"cpu": "x64_windows"},
+    visibility = ["//visibility:public"],
+)
+
+config_setting(
+    name = "windows_msvc",
+    values = {"cpu": "x64_windows_msvc"},
+    visibility = ["//visibility:public"],
+)
+
+boringssl_copts = select({
+    ":windows": [
+        "-DWIN32_LEAN_AND_MEAN",
+    ],
+    "//conditions:default": [
+        # Assembler option --noexecstack adds .note.GNU-stack to each object to
+        # ensure that binaries can be built with non-executable stack.
+        "-Wa,--noexecstack",
+
+        # This is needed on Linux systems (at least) to get rwlock in pthread.
+        "-D_XOPEN_SOURCE=700",
+
+        # This list of warnings should match those in the top-level CMakeLists.txt.
+        "-Wall",
+        "-Werror",
+        "-Wformat=2",
+        "-Wsign-compare",
+        "-Wmissing-field-initializers",
+        "-Wwrite-strings",
+        "-Wshadow",
+        "-fno-common",
+
+        # Modern build environments should be able to set this to use atomic
+        # operations for reference counting rather than locks. However, it's
+        # known not to work on some Android builds.
+        # "-DOPENSSL_C11_ATOMIC",
+    ],
+}) + select({
     ":linux_x86_64": [],
     ":mac_x86_64": [],
     "//conditions:default": ["-DOPENSSL_NO_ASM"],
@@ -75,18 +92,26 @@ crypto_sources_asm = select({
 })
 
 # For C targets only (not C++), compile with C11 support.
-boringssl_copts_c11 = boringssl_copts + [
-    "-std=c11",
-    "-Wmissing-prototypes",
-    "-Wold-style-definition",
-    "-Wstrict-prototypes",
-]
+boringssl_copts_c11 = boringssl_copts + select({
+    ":windows": [],
+    ":windows_msvc": [],
+    "//conditions:default": [
+        "-std=c11",
+        "-Wmissing-prototypes",
+        "-Wold-style-definition",
+        "-Wstrict-prototypes",
+    ],
+})
 
 # For C targets only (not C++), compile with C11 support.
-boringssl_copts_cxx = boringssl_copts + [
-    "-std=c++11",
-    "-Wmissing-declarations",
-]
+boringssl_copts_cxx = boringssl_copts + select({
+    ":windows": [],
+    ":windows_msvc": [],
+    "//conditions:default": [
+        "-std=c++11",
+        "-Wmissing-declarations",
+    ],
+})
 
 cc_library(
     name = "crypto",
@@ -96,6 +121,8 @@ cc_library(
     includes = ["src/include"],
     linkopts = select({
         ":mac_x86_64": [],
+        ":windows": [],
+        ":windows_msvc": [],
         "//conditions:default": ["-lpthread"],
     }),
     visibility = ["//visibility:public"],