diff --git a/grudge/op.py b/grudge/op.py
index 7843d67f11a8b6077a3c558753d716a2ce9cc754..f38b466a09a2bf548359d8a5b674628dc92ca6fc 100644
--- a/grudge/op.py
+++ b/grudge/op.py
@@ -832,7 +832,7 @@ def face_mass(dcoll: DiscretizationCollection, *args):
 
     .. math::
 
-        \sum_{f=1}^{N_{\text{faces}}} \mathbf{M}_{f, E}\mathbf{f}|_f,
+        \sum_{f=1}^{N_{\text{faces}} } \mathbf{M}_{f, E}\mathbf{f}|_f,
 
     where