diff --git a/t/check-non-portable-shell.pl b/t/check-non-portable-shell.pl
index f6dbe28b19..d5823f71d8 100755
--- a/t/check-non-portable-shell.pl
+++ b/t/check-non-portable-shell.pl
@@ -7,17 +7,34 @@ use strict;
 use warnings;
 
 my $exit_code=0;
+my %func;
 
 sub err {
 	my $msg = shift;
 	s/^\s+//;
 	s/\s+$//;
+	s/\s+/ /g;
 	print "$ARGV:$.: error: $msg: $_\n";
 	$exit_code = 1;
 }
 
+# glean names of shell functions
+for my $i (@ARGV) {
+	open(my $f, '<', $i) or die "$0: $i: $!\n";
+	while (<$f>) {
+		$func{$1} = 1 if /^\s*(\w+)\s*\(\)\s*{\s*$/;
+	}
+	close $f;
+}
+
 while (<>) {
 	chomp;
+	# stitch together incomplete lines (those ending with "\")
+	while (s/\\$//) {
+		$_ .= readline;
+		chomp;
+	}
+
 	/\bsed\s+-i/ and err 'sed -i is not portable';
 	/\becho\s+-[neE]/ and err 'echo with option is not portable (use printf)';
 	/^\s*declare\s+/ and err 'arrays/declare not portable';
@@ -25,6 +42,8 @@ while (<>) {
 	/\btest\s+[^=]*==/ and err '"test a == b" is not portable (use =)';
 	/\bwc -l.*"\s*=/ and err '`"$(wc -l)"` is not portable (use test_line_count)';
 	/\bexport\s+[A-Za-z0-9_]*=/ and err '"export FOO=bar" is not portable (use FOO=bar && export FOO)';
+	/^\s*([A-Z0-9_]+=(\w+|(["']).*?\3)\s+)+(\w+)/ and exists($func{$4}) and
+		err '"FOO=bar shell_func" assignment extends beyond "shell_func"';
 	# this resets our $. for each file
 	close ARGV if eof;
 }