diff --git a/randr/rrscreen.c b/randr/rrscreen.c
index d6c499580..0c70b28dd 100644
--- a/randr/rrscreen.c
+++ b/randr/rrscreen.c
@@ -558,7 +558,7 @@ rrGetScreenResources(ClientPtr client, Bool query)
 
         extraLen = rep.length << 2;
         if (extraLen) {
-            extra = malloc(extraLen);
+            extra = calloc(1, extraLen);
             if (!extra) {
                 free(modes);
                 return BadAlloc;