diff --git a/Xi/extinit.c b/Xi/extinit.c
index a2c807b46..b43f9bbc0 100644
--- a/Xi/extinit.c
+++ b/Xi/extinit.c
@@ -409,7 +409,7 @@ static int
 ProcIDispatch(ClientPtr client)
 {
     REQUEST(xReq);
-    if (stuff->data > ARRAY_SIZE(ProcIVector) || !ProcIVector[stuff->data])
+    if (stuff->data >= ARRAY_SIZE(ProcIVector) || !ProcIVector[stuff->data])
         return BadRequest;
 
     return (*ProcIVector[stuff->data])(client);
@@ -428,7 +428,7 @@ static int
 SProcIDispatch(ClientPtr client)
 {
     REQUEST(xReq);
-    if (stuff->data > ARRAY_SIZE(SProcIVector) || !SProcIVector[stuff->data])
+    if (stuff->data >= ARRAY_SIZE(SProcIVector) || !SProcIVector[stuff->data])
         return BadRequest;
 
     return (*SProcIVector[stuff->data])(client);