diff --git a/pdfminer/layout.py b/pdfminer/layout.py
index af79a85..9b7e030 100644
--- a/pdfminer/layout.py
+++ b/pdfminer/layout.py
@@ -348,7 +348,7 @@ class LTTextLineHorizontal(LTTextLine):
 
     def add(self, obj):
         if isinstance(obj, LTChar) and self.word_margin:
-            margin = self.word_margin * obj.width
+            margin = self.word_margin * max(obj.width, obj.height)
             if self._x1 < obj.x0-margin:
                 LTContainer.add(self, LTAnon(' '))
         self._x1 = obj.x1
@@ -373,7 +373,7 @@ class LTTextLineVertical(LTTextLine):
 
     def add(self, obj):
         if isinstance(obj, LTChar) and self.word_margin:
-            margin = self.word_margin * obj.height
+            margin = self.word_margin * max(obj.width, obj.height)
             if obj.y1+margin < self._y0:
                 LTContainer.add(self, LTAnon(' '))
         self._y0 = obj.y0