diff --git a/internal/buffer/settings.go b/internal/buffer/settings.go
index 156d842f..e04d7061 100644
--- a/internal/buffer/settings.go
+++ b/internal/buffer/settings.go
@@ -10,9 +10,11 @@ func (b *Buffer) SetOptionNative(option string, nativeValue interface{}) error {
 
 	if option == "fastdirty" {
 		if !nativeValue.(bool) {
-			e := calcHash(b, &b.origHash)
-			if e == ErrFileTooLarge {
-				b.Settings["fastdirty"] = false
+			if !b.Modified() {
+				e := calcHash(b, &b.origHash)
+				if e == ErrFileTooLarge {
+					b.Settings["fastdirty"] = false
+				}
 			}
 		}
 	} else if option == "statusline" {