diff --git a/mu4e/mu4e-compose.el b/mu4e/mu4e-compose.el
index ab79113a..12442033 100644
--- a/mu4e/mu4e-compose.el
+++ b/mu4e/mu4e-compose.el
@@ -397,9 +397,11 @@ set, this simply executes `fill-paragraph'."
   (if mu4e-compose-format-flowed
     (let ((fill-column (point-max))
        (use-hard-newlines nil)); rfill "across" hard newlines
-      (delete-trailing-whitespace)
+      (when (use-region-p)
+        (delete-trailing-whitespace (region-beginning) (region-end)))
       (fill-paragraph nil region))
-    (delete-trailing-whitespace)
+    (when (use-region-p)
+      (delete-trailing-whitespace (region-beginning) (region-end)))
     (fill-paragraph nil region)))
 
 (defun mu4e-toggle-use-hard-newlines ()