diff --git a/src/pyj/read_book/flow_mode.pyj b/src/pyj/read_book/flow_mode.pyj
index 5393728c24..b50a7f7dfa 100644
--- a/src/pyj/read_book/flow_mode.pyj
+++ b/src/pyj/read_book/flow_mode.pyj
@@ -12,7 +12,13 @@ from utils import document_height, viewport_to_document
 
 
 def line_height():
-    return parseFloat(line_height.doc_style.lineHeight)
+    try:
+        # will fail if line-height = "normal"
+        lh = parseFloat(line_height.doc_style.lineHeight)
+    except:
+        lh = 1.2 * parseFloat(line_height.doc_style.fontSize)
+
+    return lh
 
 def flow_to_scroll_fraction(frac, on_initial_load):
     scroll_viewport.scroll_to(0, document_height() * frac)
diff --git a/src/pyj/read_book/settings.pyj b/src/pyj/read_book/settings.pyj
index adfb516d6d..0c5defb9dd 100644
--- a/src/pyj/read_book/settings.pyj
+++ b/src/pyj/read_book/settings.pyj
@@ -9,7 +9,7 @@ from session import defaults
 opts = {}
 
 def update_settings(settings):
-    settings = settings or defaults
+    settings = Object.assign({}, defaults, settings)
     opts.base_font_size = max(8, min(settings.base_font_size, 64))
     opts.bg_image_fade = settings.bg_image_fade or 'transparent'
     opts.color_scheme = settings.color_scheme