diff --git a/dix/extension.c b/dix/extension.c
index d6d9cd39f..52bf19e64 100644
--- a/dix/extension.c
+++ b/dix/extension.c
@@ -69,8 +69,55 @@ int lastEvent = EXTENSION_EVENT_BASE;
 static int lastError = FirstExtensionError;
 static unsigned int NumExtensions = RESERVED_EXTENSIONS;
 
+static struct { const char *name; int id; } reservedExt[] = {
+    { "BIG-REQUESTS",               EXTENSION_MAJOR_BIG_REQUESTS },
+    { "Apple-WM",                   EXTENSION_MAJOR_APPLE_WM },
+    { "Apple-DRI",                  EXTENSION_MAJOR_APPLE_DRI },
+    { "Composite",                  EXTENSION_MAJOR_COMPOSITE },
+    { "DAMAGE",                     EXTENSION_MAJOR_DAMAGE },
+    { "DOUBLE-BUFFER",              EXTENSION_MAJOR_DOUBLE_BUFFER },
+    { "DPMS",                       EXTENSION_MAJOR_DPMS },
+    { "DRI2",                       EXTENSION_MAJOR_DRI2 },
+    { "DRI3",                       EXTENSION_MAJOR_DRI3 },
+    { "Generic Event Extension",    EXTENSION_MAJOR_GENERIC_EVENT },
+    { "GLX",                        EXTENSION_MAJOR_GLX },
+    { "MIT-SCREEN-SAVER",           EXTENSION_MAJOR_MIT_SCREEN_SAVER },
+    { "NAMESPACE",                  EXTENSION_MAJOR_NAMESPACE },
+    { "Present",                    EXTENSION_MAJOR_PRESENT },
+    { "RANDR",                      EXTENSION_MAJOR_RANDR },
+    { "RECORD",                     EXTENSION_MAJOR_RECORD },
+    { "RENDER",                     EXTENSION_MAJOR_RENDER },
+    { "SECURITY",                   EXTENSION_MAJOR_SECURITY },
+    { "SELinux",                    EXTENSION_MAJOR_SELINUX },
+    { "SHAPE",                      EXTENSION_MAJOR_SHAPE },
+    { "MIT-SHM",                    EXTENSION_MAJOR_SHM },
+    { "SYNC",                       EXTENSION_MAJOR_SYNC },
+    { "Windows-DRI",                EXTENSION_MAJOR_WINDOWS_DRI },
+    { "XFIXES",                     EXTENSION_MAJOR_XFIXES },
+    { "XFree86-Bigfont",            EXTENSION_MAJOR_XF86_BIGFONT },
+    { "XFree86-DGA",                EXTENSION_MAJOR_XF86_DGA },
+    { "XFree86-DRI",                EXTENSION_MAJOR_XF86_DRI },
+    { "XFree86-VidModeExtension",   EXTENSION_MAJOR_XF86_VIDMODE },
+    { "XC-MISC",                    EXTENSION_MAJOR_XC_MISC },
+    { "XInputExtension",            EXTENSION_MAJOR_XINPUT },
+    { "XINERAMA",                   EXTENSION_MAJOR_XINERAMA },
+    { "XKEYBOARD",                  EXTENSION_MAJOR_XKEYBOARD },
+    { "X-Resource",                 EXTENSION_MAJOR_XRESOURCE },
+    { "XTEST",                      EXTENSION_MAJOR_XTEST },
+    { "XVideo",                     EXTENSION_MAJOR_XVIDEO },
+    { "XVideo-MotionCompensation",  EXTENSION_MAJOR_XVMC },
+    { "XWAYLAND",                   EXTENSION_MAJOR_XWAYLAND },
+};
+
 static int checkReserved(const char* name)
 {
+    for (int i=0; i<ARRAY_SIZE(reservedExt); i++) {
+        if (strcmp(name, reservedExt[i].name) == 0) {
+            if (reservedExt[i].id < (RESERVED_EXTENSIONS + EXTENSION_BASE))
+                return reservedExt[i].id;
+            FatalError("BUG: RESERVED_EXTENSIONS too small for %d\n", reservedExt[i].id);
+        }
+    }
     return -1;
 }
 
diff --git a/dix/extension_priv.h b/dix/extension_priv.h
index b0c768485..71764ba0c 100644
--- a/dix/extension_priv.h
+++ b/dix/extension_priv.h
@@ -7,6 +7,44 @@
 
 #include "misc.h"
 
-#define RESERVED_EXTENSIONS                 2
+#define EXTENSION_MAJOR_APPLE_WM            (EXTENSION_BASE + 0)
+#define EXTENSION_MAJOR_APPLE_DRI           (EXTENSION_BASE + 1)
+#define EXTENSION_MAJOR_BIG_REQUESTS        (EXTENSION_BASE + 2)
+#define EXTENSION_MAJOR_COMPOSITE           (EXTENSION_BASE + 3)
+#define EXTENSION_MAJOR_DAMAGE              (EXTENSION_BASE + 4)
+#define EXTENSION_MAJOR_DOUBLE_BUFFER       (EXTENSION_BASE + 5)
+#define EXTENSION_MAJOR_DPMS                (EXTENSION_BASE + 6)
+#define EXTENSION_MAJOR_DRI2                (EXTENSION_BASE + 7)
+#define EXTENSION_MAJOR_DRI3                (EXTENSION_BASE + 8)
+#define EXTENSION_MAJOR_GENERIC_EVENT       (EXTENSION_BASE + 9)
+#define EXTENSION_MAJOR_GLX                 (EXTENSION_BASE + 10)
+#define EXTENSION_MAJOR_MIT_SCREEN_SAVER    (EXTENSION_BASE + 11)
+#define EXTENSION_MAJOR_NAMESPACE           (EXTENSION_BASE + 12)
+#define EXTENSION_MAJOR_PRESENT             (EXTENSION_BASE + 13)
+#define EXTENSION_MAJOR_RANDR               (EXTENSION_BASE + 14)
+#define EXTENSION_MAJOR_RECORD              (EXTENSION_BASE + 15)
+#define EXTENSION_MAJOR_RENDER              (EXTENSION_BASE + 16)
+#define EXTENSION_MAJOR_SECURITY            (EXTENSION_BASE + 17)
+#define EXTENSION_MAJOR_SELINUX             (EXTENSION_BASE + 18)
+#define EXTENSION_MAJOR_SHAPE               (EXTENSION_BASE + 19)
+#define EXTENSION_MAJOR_SHM                 (EXTENSION_BASE + 20)
+#define EXTENSION_MAJOR_SYNC                (EXTENSION_BASE + 21)
+#define EXTENSION_MAJOR_WINDOWS_DRI         (EXTENSION_BASE + 22)
+#define EXTENSION_MAJOR_XFIXES              (EXTENSION_BASE + 23)
+#define EXTENSION_MAJOR_XF86_BIGFONT        (EXTENSION_BASE + 24)
+#define EXTENSION_MAJOR_XF86_DGA            (EXTENSION_BASE + 25)
+#define EXTENSION_MAJOR_XF86_DRI            (EXTENSION_BASE + 26)
+#define EXTENSION_MAJOR_XF86_VIDMODE        (EXTENSION_BASE + 27)
+#define EXTENSION_MAJOR_XC_MISC             (EXTENSION_BASE + 28)
+#define EXTENSION_MAJOR_XINPUT              (EXTENSION_BASE + 29)
+#define EXTENSION_MAJOR_XINERAMA            (EXTENSION_BASE + 30)
+#define EXTENSION_MAJOR_XKEYBOARD           (EXTENSION_BASE + 31)
+#define EXTENSION_MAJOR_XRESOURCE           (EXTENSION_BASE + 32)
+#define EXTENSION_MAJOR_XTEST               (EXTENSION_BASE + 33)
+#define EXTENSION_MAJOR_XVIDEO              (EXTENSION_BASE + 34)
+#define EXTENSION_MAJOR_XVMC                (EXTENSION_BASE + 35)
+#define EXTENSION_MAJOR_XWAYLAND            (EXTENSION_BASE + 36)
+
+#define RESERVED_EXTENSIONS                 38
 
 #endif /* _XSERVER_EXTENSION_PRIV_H */