diff --git a/contrib/diff-highlight/diff-highlight b/contrib/diff-highlight/diff-highlight
index ffefc31a98..9280c88800 100755
--- a/contrib/diff-highlight/diff-highlight
+++ b/contrib/diff-highlight/diff-highlight
@@ -21,6 +21,10 @@ my $RESET = "\x1b[m";
 my $COLOR = qr/\x1b\[[0-9;]*m/;
 my $BORING = qr/$COLOR|\s/;
 
+# The patch portion of git log -p --graph should only ever have preceding | and
+# not / or \ as merge history only shows up on the commit line.
+my $GRAPH = qr/$COLOR?\|$COLOR?\s+/;
+
 my @removed;
 my @added;
 my $in_hunk;
@@ -32,12 +36,12 @@ $SIG{PIPE} = 'DEFAULT';
 while (<>) {
 	if (!$in_hunk) {
 		print;
-		$in_hunk = /^$COLOR*\@/;
+		$in_hunk = /^$GRAPH*$COLOR*\@/;
 	}
-	elsif (/^$COLOR*-/) {
+	elsif (/^$GRAPH*$COLOR*-/) {
 		push @removed, $_;
 	}
-	elsif (/^$COLOR*\+/) {
+	elsif (/^$GRAPH*$COLOR*\+/) {
 		push @added, $_;
 	}
 	else {
@@ -46,7 +50,7 @@ while (<>) {
 		@added = ();
 
 		print;
-		$in_hunk = /^$COLOR*[\@ ]/;
+		$in_hunk = /^$GRAPH*$COLOR*[\@ ]/;
 	}
 
 	# Most of the time there is enough output to keep things streaming,
@@ -163,6 +167,9 @@ sub highlight_pair {
 	}
 }
 
+# we split either by $COLOR or by character. This has the side effect of
+# leaving in graph cruft. It works because the graph cruft does not contain "-"
+# or "+"
 sub split_line {
 	local $_ = shift;
 	return utf8::decode($_) ?
@@ -211,8 +218,8 @@ sub is_pair_interesting {
 	my $suffix_a = join('', @$a[($sa+1)..$#$a]);
 	my $suffix_b = join('', @$b[($sb+1)..$#$b]);
 
-	return $prefix_a !~ /^$COLOR*-$BORING*$/ ||
-	       $prefix_b !~ /^$COLOR*\+$BORING*$/ ||
+	return $prefix_a !~ /^$GRAPH*$COLOR*-$BORING*$/ ||
+	       $prefix_b !~ /^$GRAPH*$COLOR*\+$BORING*$/ ||
 	       $suffix_a !~ /^$BORING*$/ ||
 	       $suffix_b !~ /^$BORING*$/;
 }
diff --git a/contrib/diff-highlight/t/t9400-diff-highlight.sh b/contrib/diff-highlight/t/t9400-diff-highlight.sh
index 1537c69d52..e42ff31f3d 100755
--- a/contrib/diff-highlight/t/t9400-diff-highlight.sh
+++ b/contrib/diff-highlight/t/t9400-diff-highlight.sh
@@ -209,7 +209,7 @@ test_expect_failure 'diff-highlight highlights mismatched hunk size' '
 
 # TODO add multi-byte test
 
-test_expect_failure 'diff-highlight works with the --graph option' '
+test_expect_success 'diff-highlight works with the --graph option' '
 	dh_test_setup_history &&
 
 	# topo-order so that the order of the commits is the same as with --graph