diff --git a/prebuilt.py b/prebuilt.py
index df7f6e36dc..a029159ed4 100755
--- a/prebuilt.py
+++ b/prebuilt.py
@@ -92,8 +92,8 @@ def UpdateLocalFile(filename, value, key='PORTAGE_BINHOST'):
     # Strip newlines from end of line. We already add newlines below.
     line = line.rstrip("\n")
 
-    if '=' not in line:
-      # Skip any line without an equal in it and just write it out.
+    if len(line.split('=')) != 2:
+      # Skip any line that doesn't fit key=val.
       file_lines.append(line)
       continue
 
diff --git a/prebuilt_unittest.py b/prebuilt_unittest.py
index 37d24afde1..fe2387fbf7 100755
--- a/prebuilt_unittest.py
+++ b/prebuilt_unittest.py
@@ -17,7 +17,9 @@ class TestUpdateFile(unittest.TestCase):
     self.contents_str = ['# comment that should be skipped',
                          'PKGDIR="/var/lib/portage/pkgs"',
                          'PORTAGE_BINHOST="http://no.thanks.com"',
-                         'portage portage-20100310.tar.bz2']
+                         'portage portage-20100310.tar.bz2',
+                         'COMPILE_FLAGS="some_value=some_other"',
+                         ]
     temp_fd, self.version_file = tempfile.mkstemp()
     os.write(temp_fd, '\n'.join(self.contents_str))
     os.close(temp_fd)