diff --git a/dispatch/source.h b/dispatch/source.h
index b54862ea8..fa960d3c2 100644
--- a/dispatch/source.h
+++ b/dispatch/source.h
@@ -32,7 +32,7 @@
 #endif
 
 #if !defined(_WIN32)
-#include <sys/signal.h>
+#include <signal.h>
 #endif
 
 DISPATCH_ASSUME_NONNULL_BEGIN
diff --git a/os/CMakeLists.txt b/os/CMakeLists.txt
index 282af25f7..cccf97ba6 100644
--- a/os/CMakeLists.txt
+++ b/os/CMakeLists.txt
@@ -3,9 +3,10 @@
 # voucher_private.h are included in the source tarball
 
 install(FILES
-          object.h
+          generic_base.h
           generic_unix_base.h
           generic_win_base.h
+          object.h
         DESTINATION
           "${INSTALL_OS_HEADERS_DIR}")
 
diff --git a/os/generic_base.h b/os/generic_base.h
new file mode 100644
index 000000000..e85257843
--- /dev/null
+++ b/os/generic_base.h
@@ -0,0 +1,34 @@
+/*
+ * Copyright (c) 2011-2014 Apple Inc. All rights reserved.
+ *
+ * @APPLE_APACHE_LICENSE_HEADER_START@
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * @APPLE_APACHE_LICENSE_HEADER_END@
+ */
+
+#ifndef __OS_GENERIC_BASE__
+#define __OS_GENERIC_BASE__
+
+#if !defined(__BEGIN_DECLS) && !defined(__END_DECLS)
+#if defined(__cplusplus)
+#define __BEGIN_DECLS extern "C" {
+#define __END_DECLS }
+#else
+#define __BEGIN_DECLS
+#define __END_DECLS
+#endif
+#endif
+
+#endif /* __OS_GENERIC_BASE__ */
diff --git a/os/generic_unix_base.h b/os/generic_unix_base.h
index aaf6f8504..b77d2adaa 100644
--- a/os/generic_unix_base.h
+++ b/os/generic_unix_base.h
@@ -13,6 +13,8 @@
 #ifndef __OS_GENERIC_UNIX_BASE__
 #define __OS_GENERIC_UNIX_BASE__
 
+#include <os/generic_base.h>
+
 #if __has_include(<sys/sysmacros.h>)
 #include <sys/sysmacros.h>
 #endif
diff --git a/os/generic_win_base.h b/os/generic_win_base.h
index afc5f4265..af2c602ec 100644
--- a/os/generic_win_base.h
+++ b/os/generic_win_base.h
@@ -13,6 +13,8 @@
 #ifndef __OS_GENERIC_WIN_BASE__
 #define __OS_GENERIC_WIN_BASE__
 
+#include <os/generic_base.h>
+
 // Unices provide `roundup` via sys/param.h
 #define roundup(x, y) ((((x) + ((y) - 1)) / (y)) * (y))
 // Unices provide `MAX` via sys/param.h
@@ -25,14 +27,6 @@
 typedef int mode_t;
 typedef void pthread_attr_t;
 
-#if defined(__cplusplus)
-#define __BEGIN_DECLS extern "C" {
-#define __END_DECLS }
-#else
-#define __BEGIN_DECLS
-#define __END_DECLS
-#endif
-
 #ifndef API_AVAILABLE
 #define API_AVAILABLE(...)
 #endif