diff --git a/NEWS.md b/NEWS.md
index 3efc5def2..0204b1bd4 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -69,6 +69,11 @@
   identifying MPLS files that refer to very short M2TS files caused mkvmerge
   to segfault.
 
+## Build system changes
+
+* [cmark](https://github.com/commonmark/cmark), the CommonMark parsing and
+  rendering library in C, is now required when building the GUIs.
+
 
 # Version 19.0.0 "Brave Captain" 2017-12-17
 
diff --git a/README.md b/README.md
index f94a681d1..f918a346c 100644
--- a/README.md
+++ b/README.md
@@ -111,6 +111,10 @@ built. These include:
   toolkit. You need this if you want to use the MKVToolNix GUI or
   mkvinfo's GUI.
 
+- [cmark](https://github.com/commonmark/cmark) — the CommonMark
+  parsing and rendering library in C is required when building the Qt
+  GUIs.
+
 - [libFLAC](http://downloads.xiph.org/releases/flac/) for FLAC
   support (Free Lossless Audio Codec)
 
diff --git a/Rakefile b/Rakefile
index 1577272f2..b5507323e 100644
--- a/Rakefile
+++ b/Rakefile
@@ -125,7 +125,7 @@ def setup_globals
   cflags_common           += " -fsanitize=undefined"                                     if c?(:UBSAN)
   cflags_common           += " -fsanitize=address -fno-omit-frame-pointer"               if c?(:ADDRSAN)
   cflags_common           += " -Ilib/libebml -Ilib/libmatroska"                          if c?(:EBML_MATROSKA_INTERNAL)
-  cflags_common           += " #{c(:MATROSKA_CFLAGS)} #{c(:EBML_CFLAGS)} #{c(:PUGIXML_CFLAGS)} #{c(:EXTRA_CFLAGS)} #{c(:DEBUG_CFLAGS)} #{c(:PROFILING_CFLAGS)} #{c(:USER_CPPFLAGS)}"
+  cflags_common           += " #{c(:MATROSKA_CFLAGS)} #{c(:EBML_CFLAGS)} #{c(:PUGIXML_CFLAGS)} #{c(:CMARK_CFLAGS)} #{c(:EXTRA_CFLAGS)} #{c(:DEBUG_CFLAGS)} #{c(:PROFILING_CFLAGS)} #{c(:USER_CPPFLAGS)}"
   cflags_common           += " -mno-ms-bitfields -DWINVER=0x0601 -D_WIN32_WINNT=0x0601 " if $building_for[:windows] # 0x0601 = Windows 7/Server 2008 R2
   cflags_common           += " -march=i686"                                              if $building_for[:windows] && /i686/.match(c(:host))
   cflags_common           += " -fPIC "                                                   if c?(:USE_QT) && !$building_for[:windows]
@@ -968,6 +968,12 @@ $common_libs = [
   :boost_system,
 ]
 
+if c?(:USE_QT)
+  $common_libs += [
+    :cmark,
+  ]
+end
+
 # custom libraries
 $custom_libs = [
   :static,
diff --git a/ac/cmark.m4 b/ac/cmark.m4
new file mode 100644
index 000000000..0a6db3d81
--- /dev/null
+++ b/ac/cmark.m4
@@ -0,0 +1,25 @@
+dnl
+dnl Check for cmark
+dnl
+
+if test x"$have_qt" = "xyes" ; then
+  PKG_CHECK_EXISTS([libcmark],[cmark_found=yes],[cmark_found=no])
+  if test x"$cmark_found" = xyes; then
+    PKG_CHECK_MODULES([libcmark],[libcmark],[cmark_found=yes])
+    CMARK_CFLAGS="`pkg-config --cflags libcmark`"
+    CMARK_LIBS="`pkg-config --libs libcmark`"
+  fi
+
+  if test x"$cmark_found" != xyes; then
+    AC_MSG_ERROR([Could not find the cmark library])
+  fi
+
+  AC_DEFINE(HAVE_CMARK,,[define if building with cmark])
+
+else
+  CMARK_CFLAGS=""
+  CMARK_LIBS=""
+fi
+
+AC_SUBST(CMARK_CFLAGS)
+AC_SUBST(CMARK_LIBS)
diff --git a/build-config.in b/build-config.in
index 679d9baf2..ef822f49f 100644
--- a/build-config.in
+++ b/build-config.in
@@ -76,6 +76,8 @@ BOOST_FILESYSTEM_LIB = @BOOST_FILESYSTEM_LIB@
 BOOST_LDFLAGS = @BOOST_LDFLAGS@
 BOOST_REGEX_LIB = @BOOST_REGEX_LIB@
 BOOST_SYSTEM_LIB = @BOOST_SYSTEM_LIB@
+CMARK_CFLAGS = @CMARK_CFLAGS@
+CMARK_LIBS = @CMARK_LIBS@
 COMPILER_TYPE = @COMPILER_TYPE@
 COMPILER_VERSION = @COMPILER_VERSION@
 DEBUG_CFLAGS = @DEBUG_CFLAGS@
diff --git a/configure.ac b/configure.ac
index 45a7f0457..2b7f0e6a0 100644
--- a/configure.ac
+++ b/configure.ac
@@ -33,6 +33,7 @@ m4_include(ac/nlohmann_jsoncpp.m4)
 m4_include(ac/utf8cpp.m4)
 m4_include(ac/zlib.m4)
 m4_include(ac/qt5.m4)
+m4_include(ac/cmark.m4)
 m4_include(ac/gnurx.m4)
 m4_include(ac/magic.m4)
 m4_include(ac/ax_boost_base.m4)
diff --git a/debian-upstream/control b/debian-upstream/control
index d43d9c646..ea497f779 100644
--- a/debian-upstream/control
+++ b/debian-upstream/control
@@ -13,7 +13,7 @@ Build-Depends:
  libboost-regex-dev (>= 1.46), libboost-date-time-dev (>= 1.46),
  libboost-system-dev (>= 1.46), qtbase5-dev, qtbase5-dev-tools,
  qtmultimedia5-dev,
- base-files (<< 9.6) | nlohmann-json-dev (>= 2),
+ base-files (<< 9.6) | nlohmann-json-dev (>= 2), cmark,
  pkg-config, po4a, docbook-xsl, xsltproc,
  libgtest-dev
 
diff --git a/mkvtoolnix.spec b/mkvtoolnix.spec
index 47e4515d4..9267f22b6 100644
--- a/mkvtoolnix.spec
+++ b/mkvtoolnix.spec
@@ -10,7 +10,7 @@ Summary: Tools to create, alter and inspect Matroska files
 Source: %{name}-%{version}.tar.xz
 Requires: hicolor-icon-theme
 
-BuildRequires: desktop-file-utils, fdupes, file-devel, flac, flac-devel, glibc-devel, libogg-devel, libstdc++-devel, libvorbis-devel, make, pkgconfig, zlib-devel, boost-devel >= 1.46.0, po4a
+BuildRequires: desktop-file-utils, fdupes, file-devel, flac, flac-devel, glibc-devel, libogg-devel, libstdc++-devel, libvorbis-devel, make, pkgconfig, zlib-devel, boost-devel >= 1.46.0, cmark-devel, po4a
 
 %if 0%{?centos}
 BuildRequires: devtoolset-6-gcc-c++, rubygem-drake
diff --git a/tools/windows/setup_cross_compilation_env.sh b/tools/windows/setup_cross_compilation_env.sh
index df56db1ac..c107fa312 100755
--- a/tools/windows/setup_cross_compilation_env.sh
+++ b/tools/windows/setup_cross_compilation_env.sh
@@ -50,7 +50,7 @@ MXE_TARGETS = ${HOST}
 MXE_PLUGIN_DIRS += plugins/gcc6
 JOBS = ${PARALLEL}
 
-MKVTOOLNIX_DEPENDENCIES=gettext libiconv zlib boost file flac lzo ogg pthreads vorbis
+MKVTOOLNIX_DEPENDENCIES=gettext libiconv zlib boost file flac lzo ogg pthreads vorbis cmark
 MKVTOOLNIX_DEPENDENCIES+=qtbase qttranslations qtwinextras
 
 mkvtoolnix-deps: \$(MKVTOOLNIX_DEPENDENCIES)