diff --git a/hgext/mq.py b/hgext/mq.py
--- a/hgext/mq.py
+++ b/hgext/mq.py
@@ -151,6 +151,8 @@ def inserthgheader(lines, header, value)
     return lines
 
 def insertplainheader(lines, header, value):
+    if lines and lines[0] and ':' not in lines[0]:
+        lines.insert(0, '')
     lines.insert(0, '%s: %s' % (header, value))
     return lines
 
diff --git a/tests/test-mq-header-date.t b/tests/test-mq-header-date.t
--- a/tests/test-mq-header-date.t
+++ b/tests/test-mq-header-date.t
@@ -311,6 +311,7 @@
   0: [mq]: 1.patch - test
   ==== qref -d
   Date: 9 0
+  
   Four
   
   diff -r ... 4
@@ -494,6 +495,7 @@
   ==== qref -u -d
   Date: 15 0
   From: john
+  
   Nine
   
   diff -r ... 9
diff --git a/tests/test-mq-header-from.t b/tests/test-mq-header-from.t
--- a/tests/test-mq-header-from.t
+++ b/tests/test-mq-header-from.t
@@ -250,6 +250,7 @@
   0: [mq]: 1.patch - mary
   ==== qref -u
   From: jane
+  
   Four
   
   diff -r ... 4of