diff --git a/kitty/config.py b/kitty/config.py
index d02969436..567218c11 100644
--- a/kitty/config.py
+++ b/kitty/config.py
@@ -200,7 +200,7 @@ def positive_float(x):
 
 def adjust_line_height(x):
     if x.endswith('%'):
-        return float(x[:-1]) / 100.0
+        return float(x[:-1].strip()) / 100.0
     return int(x)