diff --git a/src/pretix/base/pdf.py b/src/pretix/base/pdf.py
index 5ba2da2c8c..5f437f5d41 100644
--- a/src/pretix/base/pdf.py
+++ b/src/pretix/base/pdf.py
@@ -827,6 +827,12 @@ class Renderer:
         if o['italic']:
             font += ' I'
 
+        try:
+            ad = getAscentDescent(font, float(o['fontsize']))
+        except KeyError:  # font not known, fall back
+            logger.warning(f'Use of unknown font "{font}"')
+            font = 'Open Sans'
+
         align_map = {
             'left': TA_LEFT,
             'center': TA_CENTER,
@@ -856,7 +862,6 @@ class Renderer:
         p = Paragraph(text, style=style)
         w, h = p.wrapOn(canvas, float(o['width']) * mm, 1000 * mm)
         # p_size = p.wrap(float(o['width']) * mm, 1000 * mm)
-        ad = getAscentDescent(font, float(o['fontsize']))
         canvas.saveState()
         # The ascent/descent offsets here are not really proven to be correct, they're just empirical values to get
         # reportlab render similarly to browser canvas.