diff --git a/git-imerge b/git-imerge
index 3aa3a83..87eac6b 100755
--- a/git-imerge
+++ b/git-imerge
@@ -309,10 +309,12 @@ class GitTemporaryHead(object):
 
     """
 
-    def __enter__(self, git, message):
+    def __init__(self, git, message):
         self.git = git
         self.message = message
-        self.head_name = git.get_head_refname()
+
+    def __enter__(self):
+        self.head_name = self.git.get_head_refname()
         return self
 
     def __exit__(self, exc_type, exc_val, exc_tb):
diff --git a/t/test-conflicted b/t/test-conflicted
index e7e8a8f..262aa03 100755
--- a/t/test-conflicted
+++ b/t/test-conflicted
@@ -23,7 +23,11 @@ git checkout c
 "$GIT_IMERGE" init --name=c-d d
 "$GIT_IMERGE" list
 "$GIT_IMERGE" diagram --commits --frontier --html=imerge0.html
-"$GIT_IMERGE" autofill || true
+"$GIT_IMERGE" autofill 2>&1 | tee autofill.out
+if grep -q Traceback autofill.out
+then
+    exit 1
+fi
 "$GIT_IMERGE" diagram --commits --frontier --html=imerge1.html
 "$GIT_IMERGE" continue --edit
 echo 'cd version' >conflict.txt
@@ -36,7 +40,11 @@ GIT_EDITOR=cat "$GIT_IMERGE" simplify --goal=merge --branch=c-d-merge
 "$GIT_IMERGE" remove
 
 git checkout c
-"$GIT_IMERGE" start --goal=full --first-parent --name=c-d d || true
+"$GIT_IMERGE" start --goal=full --first-parent --name=c-d d 2>&1 | tee start.out
+if grep -q Traceback start.out
+then
+    exit 1
+fi
 "$GIT_IMERGE" diagram --commits --frontier --html=imerge3.html
 echo 'cd version' >conflict.txt
 git add conflict.txt