diff --git a/mercurial/patch.py b/mercurial/patch.py
--- a/mercurial/patch.py
+++ b/mercurial/patch.py
@@ -157,8 +157,8 @@ def split(stream):
             if line.split(':', 1)[0].lower() in mimeheaders:
                 # let email parser handle this
                 return mimesplit(stream, cur)
-        elif inheader:
-            # No evil headers seen, split by hand
+        elif line.startswith('--- ') and inheader:
+            # No evil headers seen by diff start, split by hand
             return headersplit(stream, cur)
         # Not enough info, keep reading
 
diff --git a/tests/test-import b/tests/test-import
--- a/tests/test-import
+++ b/tests/test-import
@@ -372,3 +372,30 @@ hg import -d '0 0' a.patch
 hg parents -v
 cd ..
 
+echo '% tricky header splitting'
+cat > trickyheaders.patch <<EOF
+From: User A <user@a>
+Subject: [PATCH] from: tricky!
+
+# HG changeset patch
+# User User B
+# Date 1266264441 18000
+# Branch stable
+# Node ID f2be6a1170ac83bf31cb4ae0bad00d7678115bc0
+# Parent  0000000000000000000000000000000000000000
+from: tricky!
+
+That is not a header.
+
+diff -r 000000000000 -r f2be6a1170ac foo
+--- /dev/null
++++ b/foo
+@@ -0,0 +1,1 @@
++foo
+EOF
+
+hg init trickyheaders
+cd trickyheaders
+hg import -d '0 0' ../trickyheaders.patch
+hg export --git tip
+cd ..
diff --git a/tests/test-import.out b/tests/test-import.out
--- a/tests/test-import.out
+++ b/tests/test-import.out
@@ -314,3 +314,20 @@ module: summary
 description
 
 
+% tricky header splitting
+applying ../trickyheaders.patch
+# HG changeset patch
+# User User B
+# Date 0 0
+# Node ID eb56ab91903632294ac504838508cb370c0901d2
+# Parent  0000000000000000000000000000000000000000
+from: tricky!
+
+That is not a header.
+
+diff --git a/foo b/foo
+new file mode 100644
+--- /dev/null
++++ b/foo
+@@ -0,0 +1,1 @@
++foo