diff --git a/openaddr/conform.py b/openaddr/conform.py
index 9a3cf6db..a25739e9 100644
--- a/openaddr/conform.py
+++ b/openaddr/conform.py
@@ -209,14 +209,20 @@ def decompress(self, source_paths, workdir, filenames):
 
         # Extract contents of zip file into expand_path directory.
         for source_path in source_paths:
-            with ZipFile(source_path, 'r') as z:
-                for name in z.namelist():
-                    if len(filenames) and not is_in(name, filenames):
-                        # Download only the named file, if any.
-                        _L.debug("Skipped file {}".format(name))
-                        continue
+            self._extract_zip(source_path, expand_path, filenames)
+
+        # Recursively extract nested zip files, but fail if more than one zip
+        # appears at the same directory level.
+        processed = set()
+        pending = list(self._find_single_zips(expand_path))
 
-                    z.extract(name, expand_path)
+        while pending:
+            zip_path = pending.pop()
+            if zip_path in processed:
+                continue
+            processed.add(zip_path)
+            self._extract_zip(zip_path, os.path.dirname(zip_path), filenames)
+            pending.extend(self._find_single_zips(os.path.dirname(zip_path)))
 
         # Collect names of directories and files in expand_path directory.
         for (dirpath, dirnames, filenames) in os.walk(expand_path):
@@ -230,6 +236,28 @@ def decompress(self, source_paths, workdir, filenames):
 
         return output_files
 
+    def _extract_zip(self, source_path, expand_path, filenames):
+        with ZipFile(source_path, 'r') as z:
+            for name in z.namelist():
+                if len(filenames) and not is_in(name, filenames):
+                    # Download only the named file, if any.
+                    _L.debug("Skipped file {}".format(name))
+                    continue
+
+                z.extract(name, expand_path)
+
+    def _find_single_zips(self, root_path):
+        zip_paths = []
+        for dirpath, _, file_names in os.walk(root_path):
+            zip_files = [name for name in file_names if name.lower().endswith('.zip')]
+            if len(zip_files) > 1:
+                raise DecompressionError(
+                    "Multiple nested zip files found in {}".format(dirpath)
+                )
+            for zip_name in zip_files:
+                zip_paths.append(os.path.join(dirpath, zip_name))
+        return zip_paths
+
 class GzipDecompressTask(DecompressionTask):
     def decompress(self, source_paths, workdir, filenames):
         output_files = []