diff --git a/lib/to_string.cc b/lib/to_string.cc
index 243d128..b246ca5 100644
--- a/lib/to_string.cc
+++ b/lib/to_string.cc
@@ -32,6 +32,10 @@ NAN_METHOD(WrappedRE2::ToString)
 	{
 		buffer += "m";
 	}
+	if (re2->dotAll)
+	{
+		buffer += "s";
+	}
 	buffer += "u";
 	if (re2->sticky)
 	{
diff --git a/tests/test_toString.js b/tests/test_toString.js
index 90e3611..1483b0a 100644
--- a/tests/test_toString.js
+++ b/tests/test_toString.js
@@ -23,6 +23,7 @@ unit.add(module, [
 		eval(t.TEST("RE2('^a{2,}', 'mi') + '' === '/^a{2,}/imu'"));
 		eval(t.TEST("RE2('^a{5}$', 'gim') + '' === '/^a{5}$/gimu'"));
 		eval(t.TEST("RE2('\\\\u{1F603}/', 'iy') + '' === '/\\\\u{1F603}\\\\//iuy'"));
+		eval(t.TEST("RE2('^a{2,}', 'smi') + '' === '/^a{2,}/imsu'"));
 
 		eval(t.TEST("RE2('c', 'ug').toString() === '/c/gu'"));
 		eval(t.TEST("RE2('d', 'um').toString() === '/d/mu'"));