diff --git a/glean/schema/cpp/schema.h b/glean/schema/cpp/schema.h
index 56941b5b4..97256f972 100644
--- a/glean/schema/cpp/schema.h
+++ b/glean/schema/cpp/schema.h
@@ -13292,7 +13292,7 @@ struct XRef {
   }
 }; // struct XRef
 
-struct FileXRefs : Predicate<std::tuple<Fact<facebook::glean::cpp::schema::Src::File>, std::vector<XRef>>> {
+struct FileXRefs : Predicate<std::tuple<Fact<facebook::glean::cpp::schema::Src::File>, std::set<XRef>>> {
   static const char* GLEAN_name() {
     return "hack.FileXRefs";
   }
diff --git a/glean/schema/source/codemarkup.hack.angle b/glean/schema/source/codemarkup.hack.angle
index e9ef5e77a..4ff994a44 100644
--- a/glean/schema/source/codemarkup.hack.angle
+++ b/glean/schema/source/codemarkup.hack.angle
@@ -41,7 +41,7 @@ predicate HackFileEntityXRefLocations:
   }
   { File, { Location, { span = Src } }, { decl = D } } where
     hack.FileXRefs { file = File, xrefs = XRefs };
-    hack.XRef { target = { declaration = D }, ranges = Uses } = XRefs[..];
+    hack.XRef { target = { declaration = D }, ranges = Uses } = elements XRefs;
     hack.DeclarationName D -> (hack.Name TargetName);
     hack.DeclarationLocation { declaration = D, file = TargetFile, span = TargetSpan };
     Location = codemarkup.types.Location { TargetName, TargetFile, { span = TargetSpan }, nothing };
@@ -56,7 +56,7 @@ predicate HackFileEntityXRefSpans:
   }
   { File, Src, { decl = D } } where
     hack.FileXRefs { file = File, xrefs = XRefs };
-    hack.XRef { target = { declaration = D }, ranges = Uses } = XRefs[..];
+    hack.XRef { target = { declaration = D }, ranges = Uses } = elements XRefs;
     Sources = prim.relToAbsByteSpans Uses;
     Src = Sources[..]
 
@@ -889,13 +889,13 @@ predicate ConvertCalleeForFileCall :
    { occurrence = {method = {name = N} } } = O;
    hack.FileXRefs { File, XRefs };
    # Look for resolved occurrences with the same method name in the call
-   { target = {declaration = D }, ranges = Uses } = XRefs[..];
+   { target = {declaration = D }, ranges = Uses } = elements XRefs;
    { method = { name = N } } = D;
    Sources = prim.relToAbsByteSpans Uses;
    S = Sources[..];
    src.ByteSpanContains { Span, S };
    # Match them with the unresolved occurrence
-   { target = O, ranges = OUses } = XRefs[..];
+   { target = O, ranges = OUses } = elements XRefs;
    OSources = prim.relToAbsByteSpans OUses;
    S = OSources[..];
    { just = { hack = { decl = D } } } = CodeCallee ) |
diff --git a/glean/schema/source/hack.angle b/glean/schema/source/hack.angle
index 66388cd14..dd7b0694f 100644
--- a/glean/schema/source/hack.angle
+++ b/glean/schema/source/hack.angle
@@ -498,7 +498,7 @@ type XRef =
 predicate FileXRefs :
   {
     file : src.File,
-    xrefs : [XRef],
+    xrefs : set XRef,
   }
 
 # Context-free information about an expression argument
@@ -541,7 +541,7 @@ predicate TargetUses :
   stored
   { T, File, Uses } where
   hack.FileXRefs { file = File, xrefs = XRefs };
-  hack.XRef { target = T, ranges = Uses } = XRefs[..]
+  hack.XRef { target = T, ranges = Uses } = elements XRefs
 
 # A version of 'TargetUses' with the bytespans converted from relative to
 # absolute offset format for convenience.