diff --git a/tools/check_revision.py b/tools/check_revision.py
index e9334dca2..4d96c2267 100644
--- a/tools/check_revision.py
+++ b/tools/check_revision.py
@@ -27,6 +27,10 @@ parser.add_option('-q', '--quiet',
 # The CEF root directory is the parent directory of _this_ script.
 cef_dir = os.path.abspath(os.path.join(os.path.dirname(__file__), os.pardir))
 
+if not os.path.exists(os.path.join(cef_dir, '.svn')):
+  sys.stdout.write("Not an SVN checkout.\n")
+  sys.exit(0)
+
 # Retrieve the CEF SVN info.
 cef_info = get_svn_info(cef_dir)
 if not options.quiet:
diff --git a/tools/make_version_header.py b/tools/make_version_header.py
index 080f09b83..3c85ccd98 100644
--- a/tools/make_version_header.py
+++ b/tools/make_version_header.py
@@ -60,10 +60,12 @@ def write_svn_header(header, chrome_version, cef_version, cpp_header_dir):
 
     year = get_year()
 
-    try:
-        revision = svn.get_revision()
-    except:
-        revision = git.get_svn_revision()
+    if os.path.exists(os.path.join('.', '.svn')):
+      revision = svn.get_revision()
+    elif os.path.exists(os.path.join('.', '.git')):
+      revision = git.get_svn_revision()
+    else:
+      raise Exception('Not a valid checkout')
 
     # calculate api hashes
     api_hash_calculator = cef_api_hash(cpp_header_dir, verbose = False)