diff --git a/pixelocr/image.py b/pixelocr/image.py
index 4c03c28..be70257 100644
--- a/pixelocr/image.py
+++ b/pixelocr/image.py
@@ -85,12 +85,17 @@ class Image(object):
 
         line_start = None
         prev_line_end = 0
+
+        def is_nonblank(row):
+            return row.any()
+
         for i, row in enumerate(self.bitmap):
-            if row.any():  # non-blank row
+            if is_nonblank(row):
                 if line_start is None:
                     line_start = i
-                    if line_start - prev_line_end >= min_space:
-                        yield self.child_cls.space(line_start - prev_line_end, self.width)
+                    height = line_start - prev_line_end
+                    if height >= min_space:
+                        yield self.child_cls.space(height, self.width)
             else:
                 if line_start is not None:
                     yield self.child_cls(self._data[line_start:i, :])