diff --git a/.github/workflows/ubuntu.yml b/.github/workflows/ubuntu.yml
index e8295961658731..dd9b9cdcfc4b9e 100644
--- a/.github/workflows/ubuntu.yml
+++ b/.github/workflows/ubuntu.yml
@@ -36,6 +36,12 @@ jobs:
           - test_task: check
             shared_gc: true
             configure: '--with-shared-gc=/home/runner/ruby_gc'
+            gc_name: 'default'
+          - test_task: check
+            shared_gc: true
+            shared_gc_dir: '/home/runner/ruby_gc'
+            configure: '--with-shared-gc=/home/runner/ruby_gc'
+            gc_name: 'mmtk'
           - test_task: test-bundler-parallel
             timeout: 50
           - test_task: test-bundled-gems
@@ -99,7 +105,6 @@ jobs:
 
       - name: Build shared GC
         run: |
-          echo "RUBY_GC_LIBRARY=librubygc.default.so" >> $GITHUB_ENV
           make shared-gc SHARED_GC=default
         if: ${{ matrix.shared_gc }}
 
@@ -117,6 +122,20 @@ jobs:
             ;;
           esac
 
+      - uses: actions-rust-lang/setup-rust-toolchain@v1
+      - name: Build MMTK Ruby lib
+        run: >-
+          cd ../src/gc/mmtk &&
+          cargo build --release &&
+          ldd target/release/libmmtk_ruby.so
+        if: $${{ matrix.shared_gc && matrix.gc_name == 'mmtk' }}
+
+      - name: Build shared GC (${{ matrix.gc_name }})
+        run: |
+          mkdir ${{ matrix.shared_gc_dir }} &&
+          make shared-gc SHARED_GC=${{ matrix.gc_name }} MMTK_BUILD=release
+        if: ${{ matrix.shared_gc }}
+
       - name: Set test options for skipped tests
         run: |
           set -x
@@ -140,10 +159,25 @@ jobs:
           ${TESTS:+TESTS="$TESTS"}
           ${{ !contains(matrix.test_task, 'bundle') && 'RUBYOPT=-w' || '' }}
         timeout-minutes: ${{ matrix.timeout || 40 }}
+        if: ${{ !matrix.shared_gc}}
+        env:
+          RUBY_TESTOPTS: '-q --tty=no'
+          TEST_BUNDLED_GEMS_ALLOW_FAILURES: 'typeprof'
+          PRECHECK_BUNDLED_GEMS: 'no'
+
+      - name: make ${{ matrix.test_task }}
+        run: >-
+          $SETARCH make -s ${{ matrix.test_task }}
+          ${TESTS:+TESTS="$TESTS"}
+          ${{ !contains(matrix.test_task, 'bundle') && 'RUBYOPT=-w' || '' }}
+        timeout-minutes: ${{ matrix.timeout || 40 }}
+        if: ${{ matrix.shared_gc}}
         env:
           RUBY_TESTOPTS: '-q --tty=no'
+          LD_LIBRARY_PATH: '/home/runner/work/ruby/ruby/src/gc/mmtk/target/release'
           TEST_BUNDLED_GEMS_ALLOW_FAILURES: 'typeprof'
           PRECHECK_BUNDLED_GEMS: 'no'
+          RUBY_GC_LIBRARY: 'librubygc.${{ matrix.gc_name }}.so'
 
       - name: make skipped tests
         run: |
diff --git a/common.mk b/common.mk
index 965acf6636dcf7..cf76584135c1fe 100644
--- a/common.mk
+++ b/common.mk
@@ -1905,6 +1905,10 @@ rewindable:
 
 HELP_EXTRA_TASKS = ""
 
+MMTK_BUILD=debug
+MMTK_LIB_PATH=-L$(srcdir)/gc/mmtk/target/$(MMTK_BUILD)
+MMTK_LIB=-lmmtk_ruby
+
 shared-gc: probes.h
 	$(Q) if test -z $(shared_gc_dir); then \
 		echo "You must configure with --with-shared-gc to use shared GC"; \
@@ -1913,16 +1917,14 @@ shared-gc: probes.h
 		echo "You must specify SHARED_GC with the GC to build"; \
 		exit 1; \
 	else \
+		$(Q) $(MAKEDIRS) $(shared_gc_dir)
+		echo generating $(shared_gc_dir)librubygc.$(SHARED_GC).$(SOEXT); \
 		if [ "$(SHARED_GC)" = "mmtk" ]; then \
-			echo generating $(shared_gc_dir)librubygc.$(SHARED_GC).$(SOEXT); \
-			$(LDSHARED) -I$(srcdir)/include -I$(srcdir) -I$(arch_hdrdir) $(XDLDFLAGS) -L$(srcdir)/gc/mmtk/target/debug -lmmtk_ruby $(cflags) -DBUILDING_SHARED_GC -fPIC -o $(shared_gc_dir)librubygc.$(SHARED_GC).$(SOEXT) $(srcdir)/gc/$(SHARED_GC).c; \
+			$(LDSHARED) -I$(srcdir)/include -I$(srcdir) -I$(arch_hdrdir) $(XDLDFLAGS) $(MMTK_LIB_PATH) $(cflags) -DBUILDING_SHARED_GC -fPIC -o $(shared_gc_dir)librubygc.$(SHARED_GC).$(SOEXT) $(srcdir)/gc/$(SHARED_GC).c $(MMTK_LIB); \
 		else \
-			echo generating $(shared_gc_dir)librubygc.$(SHARED_GC).$(SOEXT); \
-			$(LDSHARED) -I$(srcdir)/include -I$(srcdir) -I$(arch_hdrdir) $(XDLDFLAGS) $(MMTK_LIBS) $(cflags) -DBUILDING_SHARED_GC -fPIC -o $(shared_gc_dir)librubygc.$(SHARED_GC).$(SOEXT) $(srcdir)/gc/$(SHARED_GC).c; \
+			$(LDSHARED) -I$(srcdir)/include -I$(srcdir) -I$(arch_hdrdir) $(XDLDFLAGS) $(cflags) -DBUILDING_SHARED_GC -fPIC -o $(shared_gc_dir)librubygc.$(SHARED_GC).$(SOEXT) $(srcdir)/gc/$(SHARED_GC).c; \
 		fi; \
 	fi
-	$(Q) $(MAKEDIRS) $(shared_gc_dir)
-	$(Q) $(LDSHARED) -I$(srcdir)/include -I$(srcdir) -I$(arch_hdrdir) $(XDLDFLAGS) $(cflags) -DBUILDING_SHARED_GC -fPIC -o $(shared_gc_dir)librubygc.$(SHARED_GC).$(SOEXT) $(srcdir)/gc/$(SHARED_GC).c
 
 help: PHONY
 	$(MESSAGE_BEGIN) \