diff --git a/common/nix_candidate_source.go b/common/nix_candidate_source.go
index 0e8e051..b9da87a 100644
--- a/common/nix_candidate_source.go
+++ b/common/nix_candidate_source.go
@@ -1,13 +1,23 @@
 package common
 
+import "runtime"
+
 type NixCandidateSource struct {
-	fs Filesystem
+	fs      Filesystem
+	sources map[string]*PathSetIn
 }
 
 func NewNixCandidateSource(fs Filesystem) CandidateSource {
-	return &NixCandidateSource{fs}
+	return &NixCandidateSource{
+		fs,
+		map[string]*PathSetIn{},
+	}
 }
 
 func (s *NixCandidateSource) WhereSet(somePath string) *PathSetIn {
-	return nil
+	if runtime.GOOS == "windows" {
+		return nil
+	}
+	normalizedPath := s.fs.GetAbsolutePath(somePath)
+	return s.sources[normalizedPath]
 }