diff --git a/sphinx/templates/latex/longtable.tex.jinja b/sphinx/templates/latex/longtable.tex.jinja
index 3cc9e1e38..83790f4b2 100644
--- a/sphinx/templates/latex/longtable.tex.jinja
+++ b/sphinx/templates/latex/longtable.tex.jinja
@@ -24,14 +24,14 @@
 <% endif -%>
 \makeatletter
 <%- if table.align in ('center', 'default') %>
-  \setlength\LTleft{\@totalleftmargin plus1fill}
-  \setlength\LTright{\dimexpr\columnwidth-\@totalleftmargin-\linewidth\relax plus1fill}
+  \LTleft \@totalleftmargin plus1fill
+  \LTright\dimexpr\columnwidth-\@totalleftmargin-\linewidth\relax plus1fill
 <%- elif table.align == 'left' %>
-  \setlength\LTleft{\@totalleftmargin}
-  \setlength\LTright{\dimexpr\columnwidth-\@totalleftmargin-\linewidth\relax plus1fill}
+  \LTleft \@totalleftmargin
+  \LTright\dimexpr\columnwidth-\@totalleftmargin-\linewidth\relax plus1fill
 <%- elif table.align == 'right' %>
-  \setlength\LTleft{\@totalleftmargin plus1fill}
-  \setlength\LTright{\dimexpr\columnwidth-\@totalleftmargin-\linewidth\relax}
+  \LTleft \@totalleftmargin plus1fill
+  \LTright\dimexpr\columnwidth-\@totalleftmargin-\linewidth\relax
 <%- endif %>
 \makeatother
 \begin{longtable}<%= table.get_colspec() %>
diff --git a/tests/roots/test-latex-table/expects/longtable.tex b/tests/roots/test-latex-table/expects/longtable.tex
index f74eb080c..1fe1022b7 100644
--- a/tests/roots/test-latex-table/expects/longtable.tex
+++ b/tests/roots/test-latex-table/expects/longtable.tex
@@ -5,8 +5,8 @@
 \sphinxthistablewithglobalstyle
 \sphinxthistablewithborderlessstyle
 \makeatletter
-  \setlength\LTleft{\@totalleftmargin plus1fill}
-  \setlength\LTright{\dimexpr\columnwidth-\@totalleftmargin-\linewidth\relax plus1fill}
+  \LTleft \@totalleftmargin plus1fill
+  \LTright\dimexpr\columnwidth-\@totalleftmargin-\linewidth\relax plus1fill
 \makeatother
 \begin{longtable}{ll}
 \sphinxtoprule
diff --git a/tests/roots/test-latex-table/expects/longtable_having_align.tex b/tests/roots/test-latex-table/expects/longtable_having_align.tex
index 8a3e8a955..4a4df1824 100644
--- a/tests/roots/test-latex-table/expects/longtable_having_align.tex
+++ b/tests/roots/test-latex-table/expects/longtable_having_align.tex
@@ -4,8 +4,8 @@
 \sphinxatlongtablestart
 \sphinxthistablewithglobalstyle
 \makeatletter
-  \setlength\LTleft{\@totalleftmargin plus1fill}
-  \setlength\LTright{\dimexpr\columnwidth-\@totalleftmargin-\linewidth\relax}
+  \LTleft \@totalleftmargin plus1fill
+  \LTright\dimexpr\columnwidth-\@totalleftmargin-\linewidth\relax
 \makeatother
 \begin{longtable}{|l|l|}
 \sphinxtoprule
diff --git a/tests/roots/test-latex-table/expects/longtable_having_caption.tex b/tests/roots/test-latex-table/expects/longtable_having_caption.tex
index 603a3c108..a1aa65d7a 100644
--- a/tests/roots/test-latex-table/expects/longtable_having_caption.tex
+++ b/tests/roots/test-latex-table/expects/longtable_having_caption.tex
@@ -4,8 +4,8 @@
 \sphinxatlongtablestart
 \sphinxthistablewithglobalstyle
 \makeatletter
-  \setlength\LTleft{\@totalleftmargin plus1fill}
-  \setlength\LTright{\dimexpr\columnwidth-\@totalleftmargin-\linewidth\relax plus1fill}
+  \LTleft \@totalleftmargin plus1fill
+  \LTright\dimexpr\columnwidth-\@totalleftmargin-\linewidth\relax plus1fill
 \makeatother
 \begin{longtable}{|l|l|}
 \sphinxthelongtablecaptionisattop
diff --git a/tests/roots/test-latex-table/expects/longtable_having_problematic_cell.tex b/tests/roots/test-latex-table/expects/longtable_having_problematic_cell.tex
index 479bdfafe..240a76093 100644
--- a/tests/roots/test-latex-table/expects/longtable_having_problematic_cell.tex
+++ b/tests/roots/test-latex-table/expects/longtable_having_problematic_cell.tex
@@ -4,8 +4,8 @@
 \sphinxatlongtablestart
 \sphinxthistablewithglobalstyle
 \makeatletter
-  \setlength\LTleft{\@totalleftmargin plus1fill}
-  \setlength\LTright{\dimexpr\columnwidth-\@totalleftmargin-\linewidth\relax plus1fill}
+  \LTleft \@totalleftmargin plus1fill
+  \LTright\dimexpr\columnwidth-\@totalleftmargin-\linewidth\relax plus1fill
 \makeatother
 \begin{longtable}{|*{2}{\X{1}{2}|}}
 \sphinxtoprule
diff --git a/tests/roots/test-latex-table/expects/longtable_having_stub_columns_and_problematic_cell.tex b/tests/roots/test-latex-table/expects/longtable_having_stub_columns_and_problematic_cell.tex
index 9ae535c19..897830b1c 100644
--- a/tests/roots/test-latex-table/expects/longtable_having_stub_columns_and_problematic_cell.tex
+++ b/tests/roots/test-latex-table/expects/longtable_having_stub_columns_and_problematic_cell.tex
@@ -4,8 +4,8 @@
 \sphinxatlongtablestart
 \sphinxthistablewithglobalstyle
 \makeatletter
-  \setlength\LTleft{\@totalleftmargin plus1fill}
-  \setlength\LTright{\dimexpr\columnwidth-\@totalleftmargin-\linewidth\relax plus1fill}
+  \LTleft \@totalleftmargin plus1fill
+  \LTright\dimexpr\columnwidth-\@totalleftmargin-\linewidth\relax plus1fill
 \makeatother
 \begin{longtable}{|*{3}{\X{1}{3}|}}
 \sphinxtoprule
diff --git a/tests/roots/test-latex-table/expects/longtable_having_verbatim.tex b/tests/roots/test-latex-table/expects/longtable_having_verbatim.tex
index 029bc54c2..b9f75129c 100644
--- a/tests/roots/test-latex-table/expects/longtable_having_verbatim.tex
+++ b/tests/roots/test-latex-table/expects/longtable_having_verbatim.tex
@@ -4,8 +4,8 @@
 \sphinxatlongtablestart
 \sphinxthistablewithglobalstyle
 \makeatletter
-  \setlength\LTleft{\@totalleftmargin plus1fill}
-  \setlength\LTright{\dimexpr\columnwidth-\@totalleftmargin-\linewidth\relax plus1fill}
+  \LTleft \@totalleftmargin plus1fill
+  \LTright\dimexpr\columnwidth-\@totalleftmargin-\linewidth\relax plus1fill
 \makeatother
 \begin{longtable}{|*{2}{\X{1}{2}|}}
 \sphinxtoprule
diff --git a/tests/roots/test-latex-table/expects/longtable_having_widths.tex b/tests/roots/test-latex-table/expects/longtable_having_widths.tex
index 706061cd8..24dad79fd 100644
--- a/tests/roots/test-latex-table/expects/longtable_having_widths.tex
+++ b/tests/roots/test-latex-table/expects/longtable_having_widths.tex
@@ -4,8 +4,8 @@
 \sphinxatlongtablestart
 \sphinxthistablewithglobalstyle
 \makeatletter
-  \setlength\LTleft{\@totalleftmargin plus1fill}
-  \setlength\LTright{\dimexpr\columnwidth-\@totalleftmargin-\linewidth\relax plus1fill}
+  \LTleft \@totalleftmargin plus1fill
+  \LTright\dimexpr\columnwidth-\@totalleftmargin-\linewidth\relax plus1fill
 \makeatother
 \begin{longtable}{|\X{30}{100}|\X{70}{100}|}
 \noalign{\phantomsection\label{\detokenize{longtable:namedlongtable}}\label{\detokenize{longtable:mylongtable}}}%
diff --git a/tests/roots/test-latex-table/expects/longtable_having_widths_and_problematic_cell.tex b/tests/roots/test-latex-table/expects/longtable_having_widths_and_problematic_cell.tex
index f24ca827d..b4758caa0 100644
--- a/tests/roots/test-latex-table/expects/longtable_having_widths_and_problematic_cell.tex
+++ b/tests/roots/test-latex-table/expects/longtable_having_widths_and_problematic_cell.tex
@@ -4,8 +4,8 @@
 \sphinxatlongtablestart
 \sphinxthistablewithglobalstyle
 \makeatletter
-  \setlength\LTleft{\@totalleftmargin plus1fill}
-  \setlength\LTright{\dimexpr\columnwidth-\@totalleftmargin-\linewidth\relax plus1fill}
+  \LTleft \@totalleftmargin plus1fill
+  \LTright\dimexpr\columnwidth-\@totalleftmargin-\linewidth\relax plus1fill
 \makeatother
 \begin{longtable}{|\X{30}{100}|\X{70}{100}|}
 \sphinxtoprule
diff --git a/tests/roots/test-latex-table/expects/longtable_with_tabularcolumn.tex b/tests/roots/test-latex-table/expects/longtable_with_tabularcolumn.tex
index 57960d7e0..4c380fed7 100644
--- a/tests/roots/test-latex-table/expects/longtable_with_tabularcolumn.tex
+++ b/tests/roots/test-latex-table/expects/longtable_with_tabularcolumn.tex
@@ -5,8 +5,8 @@
 \sphinxthistablewithglobalstyle
 \sphinxthistablewithvlinesstyle
 \makeatletter
-  \setlength\LTleft{\@totalleftmargin plus1fill}
-  \setlength\LTright{\dimexpr\columnwidth-\@totalleftmargin-\linewidth\relax plus1fill}
+  \LTleft \@totalleftmargin plus1fill
+  \LTright\dimexpr\columnwidth-\@totalleftmargin-\linewidth\relax plus1fill
 \makeatother
 \begin{longtable}{|c|c|}
 \sphinxtoprule