diff --git a/Source/WTF/ChangeLog b/Source/WTF/ChangeLog
index 004754c..7555d4e 100644
--- a/Source/WTF/ChangeLog
+++ b/Source/WTF/ChangeLog
@@ -1,3 +1,9 @@
+2019-10-16  Wenson Hsieh  <wenson_hsieh@apple.com>
+
+        Unreviewed, fix the internal macOS 10.13 and 10.14 builds after r251171
+
+        * wtf/Platform.h: Add a HAVE() macro for AXClientType, which is only available on macOS 10.15+ SDKs.
+
 2019-10-15  Chris Dumez  <cdumez@apple.com>
 
         [macOS] Simplify main thread initialization
diff --git a/Source/WTF/wtf/Platform.h b/Source/WTF/wtf/Platform.h
index 0a4634f..ce1785d 100644
--- a/Source/WTF/wtf/Platform.h
+++ b/Source/WTF/wtf/Platform.h
@@ -1631,6 +1631,10 @@
 #define USE_PLATFORM_SYSTEM_FALLBACK_LIST 1
 #endif
 
+#if PLATFORM(MAC) && __MAC_OS_X_VERSION_MAX_ALLOWED >= 101500
+#define HAVE_AX_CLIENT_TYPE 1
+#endif
+
 #if (PLATFORM(MAC) && __MAC_OS_X_VERSION_MIN_REQUIRED >= 101500) || (PLATFORM(IOS) && __IPHONE_OS_VERSION_MIN_REQUIRED >= 130000) || PLATFORM(WATCHOS) || PLATFORM(APPLETV)
 #define HAVE_DESIGN_SYSTEM_UI_FONTS 1
 #endif
diff --git a/Source/WebKit/ChangeLog b/Source/WebKit/ChangeLog
index 9afb8ee..8355b86 100644
--- a/Source/WebKit/ChangeLog
+++ b/Source/WebKit/ChangeLog
@@ -1,3 +1,9 @@
+2019-10-16  Wenson Hsieh  <wenson_hsieh@apple.com>
+
+        Unreviewed, fix the internal macOS 10.13 and 10.14 builds after r251171
+
+        * Platform/spi/mac/ApplicationServicesSPI.h: Guard SPI declarations that use AXClientType with HAVE(AX_CLIENT_TYPE).
+
 2019-10-15  Carlos Garcia Campos  <cgarcia@igalia.com>
 
         [GTK][WPE] Add user messages API
diff --git a/Source/WebKit/Platform/spi/mac/ApplicationServicesSPI.h b/Source/WebKit/Platform/spi/mac/ApplicationServicesSPI.h
index a31f2da..048bdcb 100644
--- a/Source/WebKit/Platform/spi/mac/ApplicationServicesSPI.h
+++ b/Source/WebKit/Platform/spi/mac/ApplicationServicesSPI.h
@@ -33,6 +33,8 @@
 
 #else
 
+#if HAVE(AX_CLIENT_TYPE)
+
 typedef CF_ENUM(int32_t, AXClientType)
 {
     kAXClientTypeNoActiveRequestFound  = 0,
@@ -48,6 +50,8 @@
     kAXClientTypeDictation,
 };
 
+#endif // HAVE(AX_CLIENT_TYPE)
+
 typedef enum {
     AXSuspendStatusRunning = 0,
     AXSuspendStatusSuspended,
@@ -55,6 +59,8 @@
 
 #endif
 
+#if HAVE(AX_CLIENT_TYPE)
 extern AXClientType _AXGetClientForCurrentRequestUntrusted(void);
+#endif // HAVE(AX_CLIENT_TYPE)
 
 #endif // PLATFORM(MAC)