diff --git a/internal/lsp/cache/check.go b/internal/lsp/cache/check.go
index a830cc7f59..366a7afe13 100644
--- a/internal/lsp/cache/check.go
+++ b/internal/lsp/cache/check.go
@@ -249,15 +249,6 @@ func computePackageKey(id PackageID, files []source.FileHandle, m *KnownMetadata
 	return packageHandleKey(source.HashOf(b.Bytes()))
 }
 
-// hashEnv returns a hash of the snapshot's configuration.
-func hashEnv(s *snapshot) source.Hash {
-	s.view.optionsMu.Lock()
-	env := s.view.options.EnvSlice()
-	s.view.optionsMu.Unlock()
-
-	return source.Hashf("%s", env)
-}
-
 // hashConfig returns the hash for the *packages.Config.
 func hashConfig(config *packages.Config) source.Hash {
 	// TODO(adonovan): opt: don't materialize the bytes; hash them directly.
diff --git a/internal/lsp/cache/mod.go b/internal/lsp/cache/mod.go
index 8e6017648c..f9d148b737 100644
--- a/internal/lsp/cache/mod.go
+++ b/internal/lsp/cache/mod.go
@@ -223,33 +223,14 @@ func (s *snapshot) ModWhy(ctx context.Context, fh source.FileHandle) (map[string
 
 	// cache miss?
 	if !hit {
-		// TODO(adonovan): use a simpler cache of promises that
-		// is shared across snapshots. See comment at modTidyKey.
-		// We can then delete hashEnv too.
-		type modWhyKey struct {
-			// TODO(rfindley): is sessionID used to identify overlays because modWhy
-			// looks at overlay state? In that case, I am not sure that this key
-			// is actually correct. The key should probably just be URI, and
-			// invalidated in clone when any import changes.
-			sessionID string
-			env       source.Hash
-			view      string
-			mod       source.FileIdentity
-		}
-		key := modWhyKey{
-			sessionID: s.view.session.id,
-			env:       hashEnv(s),
-			mod:       fh.FileIdentity(),
-			view:      s.view.rootURI.Filename(),
-		}
-		handle, release := s.store.Handle(key, func(ctx context.Context, arg interface{}) interface{} {
+		handle := memoize.NewHandle("modWhy", func(ctx context.Context, arg interface{}) interface{} {
 			why, err := modWhyImpl(ctx, arg.(*snapshot), fh)
 			return modWhyResult{why, err}
 		})
 
 		entry = handle
 		s.mu.Lock()
-		s.modWhyHandles.Set(uri, entry, func(_, _ interface{}) { release() })
+		s.modWhyHandles.Set(uri, entry, nil)
 		s.mu.Unlock()
 	}