diff --git a/src/libvterm/CONTRIBUTING b/src/libvterm/CONTRIBUTING
new file mode 100644
index 0000000..2100d1e
--- /dev/null
+++ b/src/libvterm/CONTRIBUTING
@@ -0,0 +1,22 @@
+How to Contribute
+-----------------
+
+The main resources for this library are:
+
+  Launchpad
+    https://launchpad.net/libvterm
+
+  Freenode:
+    ##tty or #tickit on irc.freenode.net
+
+  Email:
+    Paul "LeoNerd" Evans <leonerd@leonerd.org.uk>
+
+
+Bug reports and feature requests can be sent to any of the above resources.
+
+New features, bug patches, etc.. should in the first instance be discussed via
+any of the resources listed above, before starting work on the actual code.
+There may be future plans or development already in-progress that could be
+affected so it is better to discuss the ideas first before starting work
+actually writing any code.
diff --git a/src/libvterm/Makefile b/src/libvterm/Makefile
index f231dd3..852c97f 100644
--- a/src/libvterm/Makefile
+++ b/src/libvterm/Makefile
@@ -37,13 +37,13 @@
 HFILES_INT=$(sort $(wildcard src/*.h)) $(HFILES)
 
 VERSION_MAJOR=0
-VERSION_MINOR=0
+VERSION_MINOR=1
 
 VERSION_CURRENT=0
 VERSION_REVISION=0
 VERSION_AGE=0
 
-VERSION=0
+VERSION=$(VERSION_MAJOR).$(VERSION_MINOR)
 
 PREFIX=/usr/local
 BINDIR=$(PREFIX)/bin
@@ -110,13 +110,11 @@
 
 # DIST CUT
 
-VERSION=$(VERSION_MAJOR).$(VERSION_MINOR)
-
 DISTDIR=libvterm-$(VERSION)
 
 distdir: $(INCFILES)
 	mkdir __distdir
-	cp LICENSE __distdir
+	cp LICENSE CONTRIBUTING __distdir
 	mkdir __distdir/src
 	cp src/*.c src/*.h src/*.inc __distdir/src
 	mkdir __distdir/src/encoding
diff --git a/src/libvterm/doc/seqs.txt b/src/libvterm/doc/seqs.txt
index 164120c..c03fa51 100644
--- a/src/libvterm/doc/seqs.txt
+++ b/src/libvterm/doc/seqs.txt
@@ -167,6 +167,7 @@
 123   SGR 1            = Bold on
       SGR 3            = Italic on
 123   SGR 4            = Underline single
+      SGR 4:x          = Underline style
 123   SGR 5            = Blink on
 123   SGR 7            = Reverse on
       SGR 9            = Strikethrough on
diff --git a/src/libvterm/include/vterm.h b/src/libvterm/include/vterm.h
index b069521..0d64166 100644
--- a/src/libvterm/include/vterm.h
+++ b/src/libvterm/include/vterm.h
@@ -19,6 +19,12 @@
 typedef unsigned char		uint8_t;
 typedef unsigned int		uint32_t;
 
+#define VTERM_VERSION_MAJOR 0
+#define VTERM_VERSION_MINOR 1
+
+#define VTERM_CHECK_VERSION \
+        vterm_check_version(VTERM_VERSION_MAJOR, VTERM_VERSION_MINOR)
+
 typedef struct VTerm VTerm;
 typedef struct VTermState VTermState;
 typedef struct VTermScreen VTermScreen;
@@ -175,6 +181,8 @@
   void  (*free)(void *ptr, void *allocdata);
 } VTermAllocatorFunctions;
 
+void vterm_check_version(int major, int minor);
+
 // Allocate and initialize a new terminal with default allocators.
 VTerm *vterm_new(int rows, int cols);
 
@@ -330,6 +338,13 @@
     unsigned int dhl       : 2; // On a DECDHL line (1=top 2=bottom)
 } VTermScreenCellAttrs;
 
+enum {
+  VTERM_UNDERLINE_OFF,
+  VTERM_UNDERLINE_SINGLE,
+  VTERM_UNDERLINE_DOUBLE,
+  VTERM_UNDERLINE_CURLY,
+};
+
 typedef struct {
 #define VTERM_MAX_CHARS_PER_CELL 6
   uint32_t chars[VTERM_MAX_CHARS_PER_CELL];
diff --git a/src/libvterm/src/pen.c b/src/libvterm/src/pen.c
index d34599d..5619f27 100644
--- a/src/libvterm/src/pen.c
+++ b/src/libvterm/src/pen.c
@@ -261,9 +261,26 @@
       setpenattr_bool(state, VTERM_ATTR_ITALIC, 1);
       break;
 
-    case 4: // Underline single
-      state->pen.underline = 1;
-      setpenattr_int(state, VTERM_ATTR_UNDERLINE, 1);
+    case 4: // Underline
+      state->pen.underline = VTERM_UNDERLINE_SINGLE;
+      if(CSI_ARG_HAS_MORE(args[argi])) {
+        argi++;
+        switch(CSI_ARG(args[argi])) {
+          case 0:
+            state->pen.underline = 0;
+            break;
+          case 1:
+            state->pen.underline = VTERM_UNDERLINE_SINGLE;
+            break;
+          case 2:
+            state->pen.underline = VTERM_UNDERLINE_DOUBLE;
+            break;
+          case 3:
+            state->pen.underline = VTERM_UNDERLINE_CURLY;
+            break;
+        }
+      }
+      setpenattr_int(state, VTERM_ATTR_UNDERLINE, state->pen.underline);
       break;
 
     case 5: // Blink
@@ -288,8 +305,8 @@
       break;
 
     case 21: // Underline double
-      state->pen.underline = 2;
-      setpenattr_int(state, VTERM_ATTR_UNDERLINE, 2);
+      state->pen.underline = VTERM_UNDERLINE_DOUBLE;
+      setpenattr_int(state, VTERM_ATTR_UNDERLINE, state->pen.underline);
       break;
 
     case 22: // Bold off
@@ -405,8 +422,10 @@
   if(state->pen.italic)
     args[argi++] = 3;
 
-  if(state->pen.underline == 1)
+  if(state->pen.underline == VTERM_UNDERLINE_SINGLE)
     args[argi++] = 4;
+  if(state->pen.underline == VTERM_UNDERLINE_CURLY)
+    args[argi++] = 4 | CSI_ARG_FLAG_MORE, args[argi++] = 3;
 
   if(state->pen.blink)
     args[argi++] = 5;
@@ -420,7 +439,7 @@
   if(state->pen.font)
     args[argi++] = 10 + state->pen.font;
 
-  if(state->pen.underline == 2)
+  if(state->pen.underline == VTERM_UNDERLINE_DOUBLE)
     args[argi++] = 21;
 
   if(state->fg_index >= 0 && state->fg_index < 8)
diff --git a/src/libvterm/src/vterm.c b/src/libvterm/src/vterm.c
index c5b6652..7b06c04 100644
--- a/src/libvterm/src/vterm.c
+++ b/src/libvterm/src/vterm.c
@@ -406,3 +406,20 @@
       (*copycell)(pos, srcpos, user);
     }
 }
+
+void vterm_check_version(int major, int minor)
+{
+  if(major != VTERM_VERSION_MAJOR) {
+    fprintf(stderr, "libvterm major version mismatch; %d (wants) != %d (library)\n",
+        major, VTERM_VERSION_MAJOR);
+    exit(1);
+  }
+
+  if(minor > VTERM_VERSION_MINOR) {
+    fprintf(stderr, "libvterm minor version mismatch; %d (wants) > %d (library)\n",
+        minor, VTERM_VERSION_MINOR);
+    exit(1);
+  }
+
+  // Happy
+}
diff --git a/src/libvterm/t/30state_pen.test b/src/libvterm/t/30state_pen.test
index 7a671e7..d1e0d14 100644
--- a/src/libvterm/t/30state_pen.test
+++ b/src/libvterm/t/30state_pen.test
@@ -28,6 +28,14 @@
   ?pen underline = 2
 PUSH "\e[24m"
   ?pen underline = 0
+PUSH "\e[4m\e[4:0m"
+  ?pen underline = 0
+PUSH "\e[4:1m"
+  ?pen underline = 1
+PUSH "\e[4:2m"
+  ?pen underline = 2
+PUSH "\e[4:3m"
+  ?pen underline = 3
 PUSH "\e[4m\e[m"
   ?pen underline = 0
 
diff --git a/src/libvterm/t/run-test.pl b/src/libvterm/t/run-test.pl
index 1b2144a..d8fbe09 100644
--- a/src/libvterm/t/run-test.pl
+++ b/src/libvterm/t/run-test.pl
@@ -177,9 +177,11 @@
 
 while( my $line = <$test> ) {
    $line =~ s/^\s+//;
-   next if $line =~ m/^(?:#|$)/;
-
    chomp $line;
+
+   next if $line =~ m/^(?:#|$)/;
+   last if $line eq "__END__";
+
    do_line( $line );
 }
 
diff --git a/src/version.c b/src/version.c
index f3f4d14..232fbb0 100644
--- a/src/version.c
+++ b/src/version.c
@@ -747,6 +747,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    785,
+/**/
     784,
 /**/
     783,