diff --git a/ext/cbson/cbson.c b/ext/cbson/cbson.c
index e75a56e..17cd4e7 100644
--- a/ext/cbson/cbson.c
+++ b/ext/cbson/cbson.c
@@ -495,7 +495,9 @@ static int write_element(VALUE key, VALUE value, VALUE extra, int allow_id) {
             }
             if (flags & MULTILINE) {
                 char multiline = 'm';
+                char dotall = 's';
                 SAFE_WRITE(buffer, &multiline, 1);
+                SAFE_WRITE(buffer, &dotall, 1);
             }
             if (flags & EXTENDED) {
                 char extended = 'x';
@@ -759,6 +761,9 @@ static VALUE get_value(const char* buffer, int* position, int type) {
                 else if (flag == 'm') {
                     flags |= MULTILINE;
                 }
+                else if (flag == 's') {
+                    flags |= MULTILINE;
+                }
                 else if (flag == 'x') {
                     flags |= EXTENDED;
                 }
diff --git a/ext/java/jar/jbson.jar b/ext/java/jar/jbson.jar
index dc5a7d8..61d1916 100644
Binary files a/ext/java/jar/jbson.jar and b/ext/java/jar/jbson.jar differ
diff --git a/ext/java/src/org/jbson/RubyBSONCallback.java b/ext/java/src/org/jbson/RubyBSONCallback.java
index b20ec2c..ed70640 100644
--- a/ext/java/src/org/jbson/RubyBSONCallback.java
+++ b/ext/java/src/org/jbson/RubyBSONCallback.java
@@ -234,6 +234,9 @@ public class RubyBSONCallback implements BSONCallback {
       if(flags.contains("m")) {
         f = f | ReOptions.RE_OPTION_MULTILINE;
       }
+      if(flags.contains("s")) {
+        f = f | ReOptions.RE_OPTION_MULTILINE;
+      }
       if(flags.contains("x")) {
         f = f | ReOptions.RE_OPTION_EXTENDED;
       }
diff --git a/ext/java/src/org/jbson/RubyBSONEncoder.java b/ext/java/src/org/jbson/RubyBSONEncoder.java
index 5b63be9..e7f8b79 100644
--- a/ext/java/src/org/jbson/RubyBSONEncoder.java
+++ b/ext/java/src/org/jbson/RubyBSONEncoder.java
@@ -642,8 +642,10 @@ public class RubyBSONEncoder extends BSONEncoder {
         if( (regexOptions & ReOptions.RE_OPTION_IGNORECASE) != 0 )
           options = options.concat( "i" );
 
-        if( (regexOptions & ReOptions.RE_OPTION_MULTILINE) != 0 )
+        if( (regexOptions & ReOptions.RE_OPTION_MULTILINE) != 0 ) {
           options = options.concat( "m" );
+          options = options.concat( "s" );
+        }
 
         if( (regexOptions & ReOptions.RE_OPTION_EXTENDED) != 0 )
           options = options.concat( "x" );
diff --git a/lib/bson/bson_ruby.rb b/lib/bson/bson_ruby.rb
index de3440f..de7bff0 100644
--- a/lib/bson/bson_ruby.rb
+++ b/lib/bson/bson_ruby.rb
@@ -343,6 +343,7 @@ module BSON
       opts = 0
       opts |= Regexp::IGNORECASE if options_str.include?('i')
       opts |= Regexp::MULTILINE if options_str.include?('m')
+      opts |= Regexp::MULTILINE if options_str.include?('s')
       opts |= Regexp::EXTENDED if options_str.include?('x')
       Regexp.new(str, opts)
     end
@@ -500,7 +501,10 @@ module BSON
       options = val.options
       options_str = ''
       options_str << 'i' if ((options & Regexp::IGNORECASE) != 0)
-      options_str << 'm' if ((options & Regexp::MULTILINE) != 0)
+      if ((options & Regexp::MULTILINE) != 0)
+        options_str << 'm'
+        options_str << 's'
+      end
       options_str << 'x' if ((options & Regexp::EXTENDED) != 0)
       options_str << val.extra_options_str if val.respond_to?(:extra_options_str)
       # Must store option chars in alphabetical order
diff --git a/test/bson/bson_test.rb b/test/bson/bson_test.rb
index 27dff22..fe2d097 100644
--- a/test/bson/bson_test.rb
+++ b/test/bson/bson_test.rb
@@ -245,6 +245,11 @@ class BSONTest < Test::Unit::TestCase
     assert_doc_pass(doc)
   end
 
+  def test_regex_multiline
+    doc = {'doc' => /foobar/m}
+    assert_doc_pass(doc)
+  end
+
   def test_boolean
     doc = {'doc' => true}
     assert_doc_pass(doc)
diff --git a/test/db_api_test.rb b/test/db_api_test.rb
index 1bb5b9c..da48803 100644
--- a/test/db_api_test.rb
+++ b/test/db_api_test.rb
@@ -396,6 +396,18 @@ class DBAPITest < Test::Unit::TestCase
     end
   end
 
+  def test_regex_multi_line
+    if @@version >= "1.9.1"
+doc = <<HERE
+  the lazy brown
+  fox
+HERE
+      @@coll.save({:doc => doc})
+      assert @@coll.find_one({:doc => /n.*x/m})
+      @@coll.remove
+    end
+  end
+
   def test_non_oid_id
     # Note: can't use Time.new because that will include fractional seconds,
     # which Mongo does not store.