diff --git a/.gitignore b/.gitignore
index 301c422..7cdc32d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -81,3 +81,4 @@
 /jdk-updates-jdk11u-jdk-11.0.11+2-4curve.tar.xz
 /jdk-updates-jdk11u-jdk-11.0.11+3-4curve.tar.xz
 /jdk-updates-jdk11u-jdk-11.0.11+4-4curve.tar.xz
+/tapsets-icedtea-6.0.0pre00-c848b93a8598.tar.xz
diff --git a/icedtea_sync.sh b/icedtea_sync.sh
index c3fd5e6..e5c54f3 100755
--- a/icedtea_sync.sh
+++ b/icedtea_sync.sh
@@ -16,12 +16,31 @@
 # You should have received a copy of the GNU Affero General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
+ICEDTEA_USE_VCS=true
+
 ICEDTEA_VERSION=3.15.0
 ICEDTEA_URL=https://icedtea.classpath.org/download/source
 ICEDTEA_SIGNING_KEY=CFDA0F9B35964222
 
+ICEDTEA_HG_URL=https://icedtea.classpath.org/hg/icedtea11
+
 set -e
 
+RPM_DIR=${PWD}
+if [ ! -f ${RPM_DIR}/jconsole.desktop.in ] ; then
+    echo "Not in RPM source tree.";
+    exit 1;
+fi
+
+if test "x${TMPDIR}" = "x"; then
+    TMPDIR=/tmp;
+fi
+WORKDIR=${TMPDIR}/it.sync
+
+echo "Using working directory ${WORKDIR}"
+mkdir ${WORKDIR}
+pushd ${WORKDIR}
+
 if test "x${WGET}" = "x"; then
     WGET=$(which wget);
     if test "x${WGET}" = "x"; then
@@ -30,68 +49,144 @@ if test "x${WGET}" = "x"; then
     fi
 fi
 
-if test "x${CHECKSUM}" = "x"; then
-    CHECKSUM=$(which sha256sum)
-    if test "x${CHECKSUM}" = "x"; then
-	echo "sha256sum not found";
-	exit 2;
-    fi
-fi
-
-if test "x${PGP}" = "x"; then
-    PGP=$(which gpg)
-    if test "x${PGP}" = "x"; then
-	echo "gpg not found";
-	exit 3;
-    fi
-fi
-
 if test "x${TAR}" = "x"; then
     TAR=$(which tar)
     if test "x${TAR}" = "x"; then
 	echo "tar not found";
-	exit 4;
+	exit 2;
     fi
 fi
 
 echo "Dependencies:";
 echo -e "\tWGET: ${WGET}";
-echo -e "\tCHECKSUM: ${CHECKSUM}";
-echo -e "\tPGP: ${PGP}\n";
 echo -e "\tTAR: ${TAR}\n";
 
-echo "Checking for IcedTea signing key ${ICEDTEA_SIGNING_KEY}...";
-if ! gpg --list-keys ${ICEDTEA_SIGNING_KEY}; then
-    echo "IcedTea signing key ${ICEDTEA_SIGNING_KEY} not installed.";
-    exit 5;
-fi
+if test "x${ICEDTEA_USE_VCS}" = "xtrue"; then
+    echo "Mode: Using VCS";
 
-echo "Downloading IcedTea release tarball...";
-${WGET} -v ${ICEDTEA_URL}/icedtea-${ICEDTEA_VERSION}.tar.xz
-echo "Downloading IcedTea tarball signature...";
-${WGET} -v ${ICEDTEA_URL}/icedtea-${ICEDTEA_VERSION}.tar.xz.sig
-echo "Downloading IcedTea tarball checksums...";
-${WGET} -v ${ICEDTEA_URL}/icedtea-${ICEDTEA_VERSION}.sha256
+    if test "x${GREP}" = "x"; then
+	GREP=$(which grep);
+	if test "x${GREP}" = "x"; then
+	    echo "grep not found";
+	    exit 3;
+	fi
+    fi
 
-echo "Verifying checksums...";
-${CHECKSUM} --check --ignore-missing icedtea-${ICEDTEA_VERSION}.sha256
+    if test "x${CUT}" = "x"; then
+	CUT=$(which cut);
+	if test "x${CUT}" = "x"; then
+	    echo "cut not found";
+	    exit 4;
+	fi
+    fi
 
-echo "Checking signature...";
-${PGP} --verify icedtea-${ICEDTEA_VERSION}.tar.xz.sig
+    if test "x${TR}" = "x"; then
+	TR=$(which tr);
+	if test "x${TR}" = "x"; then
+	    echo "tr not found";
+	    exit 5;
+	fi
+    fi
 
-echo "Extracting files...";
-${TAR} xJf icedtea-${ICEDTEA_VERSION}.tar.xz \
+    if test "x${HG}" = "x"; then
+	HG=$(which hg);
+	if test "x${HG}" = "x"; then
+	    echo "hg not found";
+	    exit 6;
+	fi
+    fi
+
+    echo "Dependencies:";
+    echo -e "\tGREP: ${GREP}";
+    echo -e "\tCUT: ${CUT}";
+    echo -e "\tTR: ${TR}";
+    echo -e "\tHG: ${HG}";
+
+    echo "Checking out repository from VCS...";
+    ${HG} clone ${ICEDTEA_HG_URL} icedtea
+
+    echo "Obtaining version from configure.ac...";
+    ROOT_VER=$(${GREP} '^AC_INIT' icedtea/configure.ac|${CUT} -d ',' -f 2|${TR} -d '[][:space:]')
+    echo "Root version from configure: ${ROOT_VER}";
+
+    VCS_REV=$(${HG} log -R icedtea --template '{node|short}' -r tip)
+    echo "VCS revision: ${VCS_REV}";
+
+    ICEDTEA_VERSION="${ROOT_VER}-${VCS_REV}"
+    echo "Creating icedtea-${ICEDTEA_VERSION}";
+    mkdir icedtea-${ICEDTEA_VERSION}
+    echo "Copying required files from checkout to icedtea-${ICEDTEA_VERSION}";
+    # Commented out for now as IcedTea 6's jconsole.desktop.in is outdated
+    #cp -a icedtea/jconsole.desktop.in ../icedtea-${ICEDTEA_VERSION}
+    cp -a ${RPM_DIR}/jconsole.desktop.in icedtea-${ICEDTEA_VERSION}
+    cp -a icedtea/tapset icedtea-${ICEDTEA_VERSION}
+
+    rm -rf icedtea
+else
+    echo "Mode: Using tarball";
+
+    if test "x${ICEDTEA_VERSION}" = "x"; then
+	echo "No IcedTea version specified for tarball download.";
+	exit 3;
+    fi
+
+    if test "x${CHECKSUM}" = "x"; then
+	CHECKSUM=$(which sha256sum)
+	if test "x${CHECKSUM}" = "x"; then
+	    echo "sha256sum not found";
+	    exit 4;
+	fi
+    fi
+
+    if test "x${PGP}" = "x"; then
+	PGP=$(which gpg)
+	if test "x${PGP}" = "x"; then
+	    echo "gpg not found";
+	    exit 5;
+	fi
+    fi
+
+    echo "Dependencies:";
+    echo -e "\tCHECKSUM: ${CHECKSUM}";
+    echo -e "\tPGP: ${PGP}\n";
+
+    echo "Checking for IcedTea signing key ${ICEDTEA_SIGNING_KEY}...";
+    if ! gpg --list-keys ${ICEDTEA_SIGNING_KEY}; then
+	echo "IcedTea signing key ${ICEDTEA_SIGNING_KEY} not installed.";
+	exit 6;
+    fi
+
+    echo "Downloading IcedTea release tarball...";
+    ${WGET} -v ${ICEDTEA_URL}/icedtea-${ICEDTEA_VERSION}.tar.xz
+    echo "Downloading IcedTea tarball signature...";
+    ${WGET} -v ${ICEDTEA_URL}/icedtea-${ICEDTEA_VERSION}.tar.xz.sig
+    echo "Downloading IcedTea tarball checksums...";
+    ${WGET} -v ${ICEDTEA_URL}/icedtea-${ICEDTEA_VERSION}.sha256
+
+    echo "Verifying checksums...";
+    ${CHECKSUM} --check --ignore-missing icedtea-${ICEDTEA_VERSION}.sha256
+
+    echo "Checking signature...";
+    ${PGP} --verify icedtea-${ICEDTEA_VERSION}.tar.xz.sig
+
+    echo "Extracting files...";
+    ${TAR} xJf icedtea-${ICEDTEA_VERSION}.tar.xz \
        icedtea-${ICEDTEA_VERSION}/tapset \
        icedtea-${ICEDTEA_VERSION}/jconsole.desktop.in
 
+    rm -vf icedtea-${ICEDTEA_VERSION}.tar.xz
+    rm -vf icedtea-${ICEDTEA_VERSION}.tar.xz.sig
+    rm -vf icedtea-${ICEDTEA_VERSION}.sha256
+fi
+
 echo "Replacing desktop files...";
-mv -v icedtea-${ICEDTEA_VERSION}/jconsole.desktop.in .
+mv -v icedtea-${ICEDTEA_VERSION}/jconsole.desktop.in ${RPM_DIR}
 
 echo "Creating new tapset tarball...";
 mv -v icedtea-${ICEDTEA_VERSION} openjdk
-${TAR} cJf tapsets-icedtea-${ICEDTEA_VERSION}.tar.xz openjdk
+${TAR} cJf ${RPM_DIR}/tapsets-icedtea-${ICEDTEA_VERSION}.tar.xz openjdk
 
 rm -rvf openjdk
-rm -vf icedtea-${ICEDTEA_VERSION}.tar.xz
-rm -vf icedtea-${ICEDTEA_VERSION}.tar.xz.sig
-rm -vf icedtea-${ICEDTEA_VERSION}.sha256
+
+popd
+rm -rf ${WORKDIR}
diff --git a/java-11-openjdk.spec b/java-11-openjdk.spec
index 2232dea..0ed654f 100644
--- a/java-11-openjdk.spec
+++ b/java-11-openjdk.spec
@@ -337,7 +337,7 @@
 %endif
 
 # Define IcedTea version used for SystemTap tapsets and desktop file
-%global icedteaver      3.15.0
+%global icedteaver      6.0.0pre00-c848b93a8598
 
 # Standard JPackage naming and versioning defines
 %global origin          openjdk
@@ -345,7 +345,7 @@
 %global top_level_dir_name   %{origin}
 %global top_level_dir_name_backup %{top_level_dir_name}-backup
 %global buildver        4
-%global rpmrelease      0
+%global rpmrelease      1
 #%%global tagsuffix      ""
 # Priority must be 8 digits in total; up to openjdk 1.8, we were using 18..... so when we moved to 11, we had to add another digit
 %if %is_system_jdk
@@ -1159,7 +1159,7 @@ URL:      http://openjdk.java.net/
 Source0: jdk-updates-jdk%{featurever}u-jdk-%{filever}+%{buildver}%{?tagsuffix:-%{tagsuffix}}-4curve.tar.xz
 
 # Use 'icedtea_sync.sh' to update the following
-# They are based on code contained in the IcedTea project (3.x).
+# They are based on code contained in the IcedTea project (6.x).
 # Systemtap tapsets. Zipped up to keep it small.
 Source8: tapsets-icedtea-%{icedteaver}.tar.xz
 
@@ -1615,11 +1615,12 @@ for suffix in %{build_loop} ; do
   for file in "tapset"$suffix/*.in; do
     OUTPUT_FILE=`echo $file | sed -e "s:\.stp\.in$:-%{version}-%{release}.%{_arch}.stp:g"`
     sed -e "s:@ABS_SERVER_LIBJVM_SO@:%{_jvmdir}/%{sdkdir -- $suffix}/lib/server/libjvm.so:g" $file > $file.1
+    sed -e "s:@JAVA_SPEC_VER@:%{javaver}:g" $file.1 > $file.2
 # TODO find out which architectures other than i686 have a client vm
 %ifarch %{ix86}
-    sed -e "s:@ABS_CLIENT_LIBJVM_SO@:%{_jvmdir}/%{sdkdir -- $suffix}/lib/client/libjvm.so:g" $file.1 > $OUTPUT_FILE
+    sed -e "s:@ABS_CLIENT_LIBJVM_SO@:%{_jvmdir}/%{sdkdir -- $suffix}/lib/client/libjvm.so:g" $file.2 > $OUTPUT_FILE
 %else
-    sed -e "/@ABS_CLIENT_LIBJVM_SO@/d" $file.1 > $OUTPUT_FILE
+    sed -e "/@ABS_CLIENT_LIBJVM_SO@/d" $file.2 > $OUTPUT_FILE
 %endif
     sed -i -e "s:@ABS_JAVA_HOME_DIR@:%{_jvmdir}/%{sdkdir -- $suffix}:g" $OUTPUT_FILE
     sed -i -e "s:@INSTALL_ARCH_DIR@:%{archinstall}:g" $OUTPUT_FILE
@@ -2283,6 +2284,10 @@ require "copy_jdk_configs.lua"
 %endif
 
 %changelog
+* Mon Mar 29 2021 Andrew Hughes <gnu.andrew@redhat.com> - 1:11.0.11.0.4-0.1.ea
+- Update tapsets from IcedTea 6.x repository with fix for JDK-8015774 changes (_heap->_heaps)
+- Update icedtea_sync.sh with a VCS mode that retrieves sources from a Mercurial repository
+
 * Mon Mar 29 2021 Andrew Hughes <gnu.andrew@redhat.com> - 1:11.0.11.0.4-0.0.ea
 - Update to jdk-11.0.11.0+4
 - Update release notes to 11.0.11.0+4
diff --git a/sources b/sources
index 23c10cf..f9ae285 100644
--- a/sources
+++ b/sources
@@ -1,2 +1,2 @@
-SHA512 (tapsets-icedtea-3.15.0.tar.xz) = c752a197cb3d812d50c35e11e4722772be40096c81d2a57933e0d9b8a3c708b9c157b8108a4e33a06ca7bb81648170994408c75d6f69d5ff12785d0c31009671
+SHA512 (tapsets-icedtea-6.0.0pre00-c848b93a8598.tar.xz) = 97d026212363b3c83f6a04100ad7f6fdde833d16579717f8756e2b8c2eb70e144a41a330cb9ccde9c3badd37a2d54fdf4650a950ec21d8b686d545ecb2a64d30
 SHA512 (jdk-updates-jdk11u-jdk-11.0.11+4-4curve.tar.xz) = d1f0cac52d0be57c9773195fe52ef79023809643dc0f80d84a0ed1f3bbddd3c08f80a69555e494137327b40ec89e6824359b56b830097a758f43575f721a06c5