diff --git a/src/resources/filters/crossref/equations.lua b/src/resources/filters/crossref/equations.lua
index 263eb8a9ca..c3ac0c1a1a 100644
--- a/src/resources/filters/crossref/equations.lua
+++ b/src/resources/filters/crossref/equations.lua
@@ -16,7 +16,7 @@ function process_equations(blockEl)
 
   -- do nothing if there is no math herein
   if inlines:find_if(isDisplayMath) == nil then
-    return blockEl
+    return nil
   end
 
   local mathInlines = nil