diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 00000000..863943d2
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,34 @@
+name: smalltalkCI
+
+on: [push, pull_request]
+
+jobs:
+  build:
+    runs-on: ubuntu-16.04
+    strategy:
+      fail-fast: false
+      matrix:
+        smalltalk: [ Pharo64-8.0, Pharo64-7.0, Pharo-6.1, Pharo-5.0, GemStone64-3.5.4, GemStone64-3.4.5, GemStone64-3.3.9, GemStone64-3.2.17, GemStone64-3.1.0.6, Squeak64-5.3, Squeak64-5.2, Squeak64-5.1 ]
+        experimental: [ false ]
+        include:
+          - smalltalk: Pharo64-9.0
+            experimental: true
+          - smalltalk: Squeak64-trunk
+            experimental: true
+    continue-on-error: ${{ matrix.experimental }}
+    name: ${{ matrix.smalltalk }}
+    steps:
+      - uses: actions/checkout@v2
+      - uses: hpi-swa/setup-smalltalkCI@v1
+        with:
+          smalltalk-version: ${{ matrix.smalltalk }}
+      - name: Fix missing OS prerequisites for GemStone builds
+        run: |
+          git clone https://github.com/GsDevKit/GsDevKit_home.git
+          ./GsDevKit_home/bin/utils/installOsPrereqs
+        continue-on-error: true
+        if: startsWith(matrix.smalltalk,'GemStone')
+      - name: Run tests
+        run: smalltalkci -s ${{ matrix.smalltalk }}
+        shell: bash
+        timeout-minutes: 10
\ No newline at end of file
diff --git a/repository/Grease-GemStone-Core.package/GRGemStonePlatform.class/instance/thisContext.st b/repository/Grease-GemStone-Core.package/GRGemStonePlatform.class/instance/thisContext.st
index 44dc34ca..50e2a5b0 100644
--- a/repository/Grease-GemStone-Core.package/GRGemStonePlatform.class/instance/thisContext.st
+++ b/repository/Grease-GemStone-Core.package/GRGemStonePlatform.class/instance/thisContext.st
@@ -1,3 +1,3 @@
 *grease-gemstone-core
 thisContext
-  ^ (GsContext fromLevel: 1) sender sender
\ No newline at end of file
+  ^ GsContext fromLevel: 3
\ No newline at end of file
diff --git a/repository/Grease-GemStone-Core.package/GsContext.class/instance/namedTempAt..st b/repository/Grease-GemStone-Core.package/GsContext.class/instance/namedTempAt..st
new file mode 100644
index 00000000..4ca86721
--- /dev/null
+++ b/repository/Grease-GemStone-Core.package/GsContext.class/instance/namedTempAt..st
@@ -0,0 +1,3 @@
+accessing
+namedTempAt: index
+  ^ self tempAt: index
\ No newline at end of file
diff --git a/repository/Grease-Tests-Core.package/GRPlatformTest.class/instance/returnSender.st b/repository/Grease-Tests-Core.package/GRPlatformTest.class/instance/returnSender.st
new file mode 100644
index 00000000..1b25f567
--- /dev/null
+++ b/repository/Grease-Tests-Core.package/GRPlatformTest.class/instance/returnSender.st
@@ -0,0 +1,3 @@
+private
+returnSender
+	^ GRPlatform current thisContext sender
\ No newline at end of file
diff --git a/repository/Grease-Tests-Core.package/GRPlatformTest.class/instance/testThisContext.st b/repository/Grease-Tests-Core.package/GRPlatformTest.class/instance/testThisContext.st
index 3cd4ceb1..fd515dd9 100644
--- a/repository/Grease-Tests-Core.package/GRPlatformTest.class/instance/testThisContext.st
+++ b/repository/Grease-Tests-Core.package/GRPlatformTest.class/instance/testThisContext.st
@@ -1,9 +1,18 @@
-tests-processes
+tests
 testThisContext
-  | methodContext |
-  methodContext := self platform thisContext.
-  [ 
-  | blockContext |
-  blockContext := self platform thisContext.
-  self assert: blockContext sender = methodContext ]
-    value
\ No newline at end of file
+	| methodContext block |
+	methodContext := self platform thisContext.
+	block := [ | blockContext |
+	blockContext := self platform thisContext.
+	self assert: blockContext sender = methodContext.
+	"The following is a difference between Gemstone and Pharo... "
+	(Smalltalk includesKey: #GRGemStonePlatform)
+		ifTrue: [ self assert: blockContext receiver = block ]
+		ifFalse: [ 
+			self assert: blockContext receiver = self.
+			self assert: (blockContext namedTempAt: (blockContext tempNames indexOf: #blockContext)) == blockContext ].
+	self assert: (blockContext namedTempAt: (blockContext tempNames indexOf: #methodContext)) == methodContext ].
+	block value.
+	self assert: self returnSender = methodContext.
+	self assert: methodContext receiver = self.
+	self assert: (self platform thisContext namedTempAt: (self platform thisContext tempNames indexOf: #block)) == block
\ No newline at end of file