diff --git a/repository/Grease-Squeak6-Core.package/GRSqueakPlatform.class/instance/thisContext.st b/repository/Grease-Squeak6-Core.package/GRSqueakPlatform.class/instance/thisContext.st
new file mode 100644
index 00000000..ed9ce368
--- /dev/null
+++ b/repository/Grease-Squeak6-Core.package/GRSqueakPlatform.class/instance/thisContext.st
@@ -0,0 +1,4 @@
+processes
+thisContext
+
+	^ thisContext sender
diff --git a/repository/Grease-Squeak6-Core.package/String.extension/instance/substrings..st b/repository/Grease-Squeak6-Core.package/String.extension/instance/substrings..st
new file mode 100644
index 00000000..90bc60ae
--- /dev/null
+++ b/repository/Grease-Squeak6-Core.package/String.extension/instance/substrings..st
@@ -0,0 +1,5 @@
+*grease-squeak6-core
+substrings: aString
+
+	^ self subStrings: aString
+
diff --git a/repository/Grease-Squeak6-Core.package/Symbol.extension/instance/greaseAsMutator.st b/repository/Grease-Squeak6-Core.package/Symbol.extension/instance/greaseAsMutator.st
new file mode 100644
index 00000000..075a4ccf
--- /dev/null
+++ b/repository/Grease-Squeak6-Core.package/Symbol.extension/instance/greaseAsMutator.st
@@ -0,0 +1,4 @@
+*grease-squeak6-core
+greaseAsMutator
+
+	^ self asSimpleSetter
diff --git a/repository/Grease-Squeak6-Core.package/Symbol.extension/properties.json b/repository/Grease-Squeak6-Core.package/Symbol.extension/properties.json
new file mode 100644
index 00000000..565e67b0
--- /dev/null
+++ b/repository/Grease-Squeak6-Core.package/Symbol.extension/properties.json
@@ -0,0 +1,2 @@
+{
+	"name" : "Symbol" }
diff --git a/repository/Grease-Tests-Squeak6-Core.package/GRPlatformTest.extension/instance/writeToFile.withFileNameDo..st b/repository/Grease-Tests-Squeak6-Core.package/GRPlatformTest.extension/instance/writeToFile.withFileNameDo..st
new file mode 100644
index 00000000..ec976216
--- /dev/null
+++ b/repository/Grease-Tests-Squeak6-Core.package/GRPlatformTest.extension/instance/writeToFile.withFileNameDo..st
@@ -0,0 +1,12 @@
+*grease-tests-squeak6-core
+writeToFile: aStringOrByteArray withFileNameDo: aBlock
+	| fileName directory |
+	fileName :=  'GRPharoPlatformTest'.
+	directory := FileSystem disk workingDirectory.
+	[ GRPlatform current
+		write: aStringOrByteArray
+		toFile: fileName
+		inFolder: directory fullName.
+	aBlock value: directory fullName, GRPlatform current pathSeparator, fileName
+		] ensure: [
+			(directory / fileName) delete ]