diff --git a/go/analysis/internal/facts/facts.go b/go/analysis/internal/facts/facts.go
index 07984521c3..1fb69c6159 100644
--- a/go/analysis/internal/facts/facts.go
+++ b/go/analysis/internal/facts/facts.go
@@ -101,11 +101,13 @@ func (s *Set) ExportObjectFact(obj types.Object, fact analysis.Fact) {
 
 func (s *Set) AllObjectFacts(filter map[reflect.Type]bool) []analysis.ObjectFact {
 	var facts []analysis.ObjectFact
+	s.mu.Lock()
 	for k, v := range s.m {
 		if k.obj != nil && filter[k.t] {
 			facts = append(facts, analysis.ObjectFact{Object: k.obj, Fact: v})
 		}
 	}
+	s.mu.Unlock()
 	return facts
 }
 
@@ -134,11 +136,13 @@ func (s *Set) ExportPackageFact(fact analysis.Fact) {
 
 func (s *Set) AllPackageFacts(filter map[reflect.Type]bool) []analysis.PackageFact {
 	var facts []analysis.PackageFact
+	s.mu.Lock()
 	for k, v := range s.m {
 		if k.obj == nil && filter[k.t] {
 			facts = append(facts, analysis.PackageFact{Package: k.pkg, Fact: v})
 		}
 	}
+	s.mu.Unlock()
 	return facts
 }