2 files changed, 49 insertions, 13 deletions
diff --git a/Master/texmf-dist/tex/latex/base/latex.ltx b/Master/texmf-dist/tex/latex/base/latex.ltx
index 09f921e2795..4b3cccd20d1 100644
--- a/Master/texmf-dist/tex/latex/base/latex.ltx
+++ b/Master/texmf-dist/tex/latex/base/latex.ltx
@@ -710,7 +710,7 @@
 \def\fmtname{LaTeX2e}
 \edef\fmtversion
    {2020-02-02}
-\def\patch@level{4}
+\def\patch@level{5}
 \edef\development@branch@name{}
 \iffalse
 \def\reserved@a#1/#2/#3\@nil{%
@@ -991,6 +991,7 @@
 \@onlypreamble\@check@eq
 \long\def \@gobble #1{}
 \long\def \@gobbletwo #1#2{}
+\long\def \@gobblethree #1#2#3{}
 \long\def \@gobblefour #1#2#3#4{}
 \long\def\@firstofone#1{#1}
 \long\def\@firstoftwo#1#2{#1}
@@ -2393,11 +2394,16 @@ Type  H <return>  for immediate help.}%
    \expandafter\ifx\csname #1+#2\endcsname\relax
      \@latex@error{Font family `#1+#2' unknown}\@eha
    \else
+     \edef\reserved@a{#3}%
+     \expandafter\series@maybe@drop@one@m\expandafter{#3}\reserved@b
+     \ifx\reserved@a\reserved@b\else
+       \@latex@warning{Font shape declaration has incorrect series
+         value `#3'.\MessageBreak It should not contain an `m'!
+         Please correct it.\MessageBreak Found}%
+     \fi
      \expandafter
-       \xdef\csname#1/#2/%
-       \expandafter\series@drop@one@m #3mm\series@drop@one@m/%
-       #4\endcsname{\expandafter\noexpand
-                                   \csname #5\endcsname}%
+       \xdef\csname#1/#2/\reserved@b/#4\endcsname
+                 {\expandafter\noexpand\csname #5\endcsname}%
      \def\reserved@a{#6}%
      \global
      \expandafter\let\csname#5\expandafter\endcsname
@@ -3297,10 +3303,22 @@ Type  H <return>  for immediate help.}%
 \DeclareFontSeriesChangeRule {m}{sc}{msc}{mc}
 \def\set@target@series#1{%
     \edef\f@series{#1}%
-    \edef\f@series{\expandafter\series@drop@one@m\f@series mm\series@drop@one@m}%
+    \expandafter\series@maybe@drop@one@m\expandafter{\f@series}\f@series
+}
+\def\series@maybe@drop@one@m#1#2{%
+  \def\in@@##1,#1,{}%
+  \series@check@toks\expandafter{\in@@
+    ,ulm,elm,lm,slm,mm,sbm,bm,ebm,ubm,muc,mec,mc,msc,msx,mx,mex,mux,{}{},#1,}%
+  \edef\in@@{\the\series@check@toks}%
+  \ifx\in@@\@empty
+    \def#2{#1}%
+  \else
+    \edef#2{\expandafter\series@drop@one@m #1m\series@drop@one@m}%
+  \fi
 }
+\newtoks\series@check@toks
 \def\series@drop@one@m#1m#2m#3\series@drop@one@m{%
-  \ifx\relax#1#2\relax m\else#1#2\fi
+   #1#2%
 }
 
 \def\DeclareFontShapeChangeRule #1#2#3#4{%
diff --git a/Master/texmf-dist/tex/latex/base/latexrelease.sty b/Master/texmf-dist/tex/latex/base/latexrelease.sty
index 11e6ea016af..353f2aa7c5f 100644
--- a/Master/texmf-dist/tex/latex/base/latexrelease.sty
+++ b/Master/texmf-dist/tex/latex/base/latexrelease.sty
@@ -4816,11 +4816,16 @@ of this package available from CTAN}
    \expandafter\ifx\csname #1+#2\endcsname\relax
      \@latex@error{Font family `#1+#2' unknown}\@eha
    \else
+     \edef\reserved@a{#3}%
+     \expandafter\series@maybe@drop@one@m\expandafter{#3}\reserved@b
+     \ifx\reserved@a\reserved@b\else
+       \@latex@warning{Font shape declaration has incorrect series
+         value `#3'.\MessageBreak It should not contain an `m'!
+         Please correct it.\MessageBreak Found}%
+     \fi
      \expandafter
-       \xdef\csname#1/#2/%
-       \expandafter\series@drop@one@m #3mm\series@drop@one@m/%
-       #4\endcsname{\expandafter\noexpand
-                                   \csname #5\endcsname}%
+       \xdef\csname#1/#2/\reserved@b/#4\endcsname
+                 {\expandafter\noexpand\csname #5\endcsname}%
      \def\reserved@a{#6}%
      \global
      \expandafter\let\csname#5\expandafter\endcsname
@@ -5538,10 +5543,22 @@ of this package available from CTAN}
 \DeclareFontSeriesChangeRule {m}{sc}{msc}{mc}
 \def\set@target@series#1{%
     \edef\f@series{#1}%
-    \edef\f@series{\expandafter\series@drop@one@m\f@series mm\series@drop@one@m}%
+    \expandafter\series@maybe@drop@one@m\expandafter{\f@series}\f@series
+}
+\def\series@maybe@drop@one@m#1#2{%
+  \def\in@@##1,#1,{}%
+  \series@check@toks\expandafter{\in@@
+    ,ulm,elm,lm,slm,mm,sbm,bm,ebm,ubm,muc,mec,mc,msc,msx,mx,mex,mux,{}{},#1,}%
+  \edef\in@@{\the\series@check@toks}%
+  \ifx\in@@\@empty
+    \def#2{#1}%
+  \else
+    \edef#2{\expandafter\series@drop@one@m #1m\series@drop@one@m}%
+  \fi
 }
+\newtoks\series@check@toks
 \def\series@drop@one@m#1m#2m#3\series@drop@one@m{%
-  \ifx\relax#1#2\relax m\else#1#2\fi
+   #1#2%
 }
 
 \def\DeclareFontShapeChangeRule #1#2#3#4{%
@@ -5667,6 +5684,7 @@ of this package available from CTAN}
 \let\@font@shape@subst@warning\@undefined
 \let\maybe@load@fontshape\@undefined
 \let\set@target@series\@undefined
+\let\series@maybe@drop@one@m\@undefined
 \let\series@drop@one@m\@undefined
 \let\DeclareFontShapeChangeRule\@undefined
 \let\merge@font@shape\@undefined