diff --git a/src/calibre/ebooks/oeb/transforms/flatcss.py b/src/calibre/ebooks/oeb/transforms/flatcss.py
index c02dfe9e34..3c12a28080 100644
--- a/src/calibre/ebooks/oeb/transforms/flatcss.py
+++ b/src/calibre/ebooks/oeb/transforms/flatcss.py
@@ -475,9 +475,10 @@ class CSSFlattener(object):
 
         try:
             minlh = self.context.minimum_line_height / 100.
-            if not is_drop_cap and style['line-height'] < minlh * fsize:
+            slh = style['line-height']
+            if not is_drop_cap and isinstance(slh, numbers.Number) and slh < minlh * fsize:
                 cssdict['line-height'] = unicode_type(minlh)
-        except:
+        except Exception:
             self.oeb.logger.exception('Failed to set minimum line-height')
 
         if cssdict:
diff --git a/src/calibre/ebooks/txt/processor.py b/src/calibre/ebooks/txt/processor.py
index e4834f7ea8..dbe6dfe9db 100644
--- a/src/calibre/ebooks/txt/processor.py
+++ b/src/calibre/ebooks/txt/processor.py
@@ -240,7 +240,7 @@ def split_string_separator(txt, size):
     '''
     Splits the text by putting \n\n at the point size.
     '''
-    if len(txt) > size:
+    if len(txt) > size and size > 2:
         size -= 2
         txt = []
         for part in (txt[i * size: (i + 1) * size] for i in range(0, len(txt), size)):