diff --git a/source/macros.tex b/source/macros.tex
index 5be88cfd6a..7a562230b8 100644
--- a/source/macros.tex
+++ b/source/macros.tex
@@ -407,7 +407,7 @@
 
 %% Change descriptions
 \newcommand{\diffhead}[1]{\textbf{#1:}\space}
-\newcommand{\diffdef}[1]{\hfill\break\diffhead{#1}}
+\newcommand{\diffdef}[1]{\ifvmode\else\hfill\break\fi\diffhead{#1}}
 \ExplSyntaxOn
 \NewDocumentCommand \diffref { m } {
   \clist_set:Nx \l_tmpa_clist { #1 }