diff --git a/kas/context.py b/kas/context.py
index a2cee02..a17bac3 100644
--- a/kas/context.py
+++ b/kas/context.py
@@ -126,3 +126,7 @@ class Context:
             The reference directory for the repo
         """
         return self.__kas_repo_ref_dir
+
+    @property
+    def force_checkout(self):
+        return getattr(self.args, 'force_checkout', None)
diff --git a/kas/kas.py b/kas/kas.py
index ab6076b..453d464 100644
--- a/kas/kas.py
+++ b/kas/kas.py
@@ -106,6 +106,9 @@ def setup_parser_common_args(parser):
     parser.add_argument('--skip',
                         help='Skip build steps',
                         default=[])
+    parser.add_argument('--force-checkout', action='store_true',
+                        help='Always checkout the desired refspec of each '
+                        'repository, discarding any local changes')
 
 def kas_get_argparser():
     """
diff --git a/kas/repos.py b/kas/repos.py
index 1e3929e..c1c3281 100644
--- a/kas/repos.py
+++ b/kas/repos.py
@@ -221,13 +221,14 @@ class RepoImpl(Repo):
         if self.operations_disabled or self.refspec is None:
             return
 
-        # Check if repos is dirty
-        (_, output) = run_cmd(self.is_dirty_cmd(),
-                              cwd=self.path,
-                              fail=False)
-        if output:
-            logging.warning('Repo %s is dirty - no checkout', self.name)
-            return
+        if not get_context().force_checkout:
+            # Check if repos is dirty
+            (_, output) = run_cmd(self.is_dirty_cmd(),
+                                  cwd=self.path,
+                                  fail=False)
+            if output:
+                logging.warning('Repo %s is dirty - no checkout', self.name)
+                return
 
         (_, output) = run_cmd(self.resolve_branch_cmd(),
                               cwd=self.path, fail=False)
@@ -359,6 +360,8 @@ class GitRepo(RepoImpl):
         cmd = ['git', 'checkout', '-q', desired_ref]
         if branch:
             cmd.extend(['-B', self.refspec])
+        if get_context().force_checkout:
+            cmd.append('--force')
         return cmd
 
     def prepare_patches_cmd(self):
@@ -400,7 +403,10 @@ class MercurialRepo(RepoImpl):
         return ['false']
 
     def checkout_cmd(self, desired_ref, branch):
-        return ['hg', 'checkout', desired_ref]
+        cmd = ['hg', 'checkout', desired_ref]
+        if get_context().force_checkout:
+            cmd.append('--clean')
+        return cmd
 
     def prepare_patches_cmd(self):
         return ['hg', 'branch', '-f',