diff --git a/packages/math/tools/unicode-xml-to-sile.xsl b/packages/math/tools/unicode-xml-to-sile.xsl
index 2a11f7457..7b0ebd626 100644
--- a/packages/math/tools/unicode-xml-to-sile.xsl
+++ b/packages/math/tools/unicode-xml-to-sile.xsl
@@ -129,8 +129,9 @@ local function addSymbol (str, shortatom, mathlatex, _, ops)
     op.forms = {}
     for _, v in pairs(ops) do
       if v.form then
-        v.lspace = SILE.types.length(v.lspace and ("%smu"):format(v.lspace) or "0mu")
-        v.rspace = SILE.types.length(v.rspace and ("%smu"):format(v.rspace) or "0mu")
+        -- NOTE: At this point the mu unit is not yet defined, so keep it as a string.
+        v.lspace = v.lspace and ("%smu"):format(v.lspace) or "0mu"
+        v.rspace = v.rspace and ("%smu"):format(v.rspace) or "0mu"
         op.forms[v.form] = v
       else
         SU.warn("No form for operator " .. str .. " (operator dictionary is probably incomplete)")
diff --git a/packages/math/unicode-symbols-generated.lua b/packages/math/unicode-symbols-generated.lua
index c2ed8d463..cdea8dfc5 100644
--- a/packages/math/unicode-symbols-generated.lua
+++ b/packages/math/unicode-symbols-generated.lua
@@ -47,8 +47,9 @@ local function addSymbol (str, shortatom, mathlatex, _, ops)
     op.forms = {}
     for _, v in pairs(ops) do
       if v.form then
-        v.lspace = SILE.types.length(v.lspace and ("%smu"):format(v.lspace) or "0mu")
-        v.rspace = SILE.types.length(v.rspace and ("%smu"):format(v.rspace) or "0mu")
+        -- NOTE: At this point the mu unit is not yet defined, so keep it as a string.
+        v.lspace = v.lspace and ("%smu"):format(v.lspace) or "0mu"
+        v.rspace = v.rspace and ("%smu"):format(v.rspace) or "0mu"
         op.forms[v.form] = v
       else
         SU.warn("No form for operator " .. str .. " (operator dictionary is probably incomplete)")