diff --git a/ast/compile.go b/ast/compile.go
index 4c268dd15a..c51951c383 100644
--- a/ast/compile.go
+++ b/ast/compile.go
@@ -618,7 +618,7 @@ func (c *Compiler) buildRuleIndices() {
 			return false
 		}
 		index := newBaseDocEqIndex(func(ref Ref) bool {
-			return len(c.GetRules(ref.GroundPrefix())) > 0
+			return isVirtual(c.RuleTree, ref.GroundPrefix())
 		})
 		if rules := extractRules(node.Values); index.Build(rules) {
 			c.ruleIndices.Put(rules[0].Path(), index)
@@ -3229,6 +3229,19 @@ func isDataRef(term *Term) bool {
 	return false
 }
 
+func isVirtual(node *TreeNode, ref Ref) bool {
+	for i := 0; i < len(ref); i++ {
+		child := node.Child(ref[i].Value)
+		if child == nil {
+			return false
+		} else if len(child.Values) > 0 {
+			return true
+		}
+		node = child
+	}
+	return true
+}
+
 func safetyErrorSlice(unsafe unsafeVars) (result Errors) {
 
 	if len(unsafe) == 0 {
diff --git a/ast/compile_test.go b/ast/compile_test.go
index 72050d5808..98649278f8 100644
--- a/ast/compile_test.go
+++ b/ast/compile_test.go
@@ -98,6 +98,10 @@ s[2] { true }`,
 	if user.Hide {
 		t.Fatalf("Expected user.system node to be visible")
 	}
+
+	if !isVirtual(tree, MustParseRef("data.a.b.empty")) {
+		t.Fatal("Expected data.a.b.empty to be virtual")
+	}
 }
 
 func TestCompilerEmpty(t *testing.T) {
diff --git a/topdown/topdown_test.go b/topdown/topdown_test.go
index f41a059262..011fc91245 100644
--- a/topdown/topdown_test.go
+++ b/topdown/topdown_test.go
@@ -756,6 +756,28 @@ p[x] = y { data.enum_errors.a[x] = y }`,
 	assertTopDownWithPath(t, compiler, store, "enumerate virtual errors", []string{"enum_errors", "caller", "p"}, `{}`, fmt.Errorf("divide by zero"))
 }
 
+func TestTopDownFix1863(t *testing.T) {
+
+	compiler := ast.MustCompileModules(map[string]string{
+		"test1.rego": `
+			package a.b
+
+			# this module is empty
+		`,
+		"test2.rego": `
+			package x
+
+			p = data.a.b  # p should be defined (an empty object)
+		`,
+	})
+
+	store := inmem.New()
+
+	assertTopDownWithPath(t, compiler, store, "is defined", []string{}, ``, `{"a": {"b": {}}, "x": {"p": {}}}`)
+	assertTopDownWithPath(t, compiler, store, "is defined", []string{"x"}, ``, `{"p": {}}`)
+	assertTopDownWithPath(t, compiler, store, "is defined", []string{"x", "p"}, ``, `{}`)
+}
+
 func TestTopDownNestedReferences(t *testing.T) {
 	tests := []struct {
 		note     string