diff --git a/macros/PGbasicmacros.pl b/macros/PGbasicmacros.pl
index 37d1f66af4..cb767c752e 100644
--- a/macros/PGbasicmacros.pl
+++ b/macros/PGbasicmacros.pl
@@ -1832,7 +1832,7 @@ sub general_math_ev3 {
 	my $mode = shift || "inline";
 
 	$in = FEQ($in); # Format EQuations
-	$in =~ s/((^|[^\\])(\\\\)*)%/\1\\%/g; # avoid % becoming TeX comments (unless already escaped)
+	$in =~ s/((^|[^\\])(\\\\)*)%/$1\\%/g; # avoid % becoming TeX comments (unless already escaped)
 
 	## remove leading and trailing spaces so that HTML mode will
 	## not include unwanted spaces as per Davide Cervone.