diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 0d1a485..1a8d763 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -18,7 +18,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        pharoversion: [ Pharo64-12, Pharo64-11, Pharo64-10 ]
+        pharoversion: [ Pharo64-alpha, Pharo64-13, Pharo64-12, Pharo64-11, Pharo64-10 ]
     name: ${{ matrix.pharoversion }}
     runs-on: ubuntu-latest
     steps:
diff --git a/repository/Mustache-Core/Object.extension.st b/repository/Mustache-Core/Object.extension.st
index 5dfd884..51c984c 100644
--- a/repository/Mustache-Core/Object.extension.st
+++ b/repository/Mustache-Core/Object.extension.st
@@ -1,7 +1,8 @@
 Extension { #name : 'Object' }
 
 { #category : '*mustache-core' }
-Object >> mustacheDefaultWhenLookupFails [
+Object >> mustacheDefaultWhenLookupFails: failingPartString [
+
 	^ nil
 ]
 
@@ -17,10 +18,14 @@ Object >> mustacheDo: aBlock inverted: aBoolean [
 
 { #category : '*mustache-core' }
 Object >> mustacheLookup: aString [
+	"The lookup supports navigation between objects using messages expressed by $. 
+	
+	For example {{{ site.configuration }}} means that the template accesses the value returned by the message configuration sent to the result of the message site."
+	
 	(aString = '.') ifTrue: [ ^ self ].
-	^ [ self perform: aString asSymbol ]
-		on: MessageNotUnderstood 
-		do: [ :err | self mustacheLookupComplex: aString  ]
+	^ (self respondsTo: aString asSymbol) 
+		ifTrue: [ self perform: aString asSymbol ]
+		ifFalse: [  self mustacheLookupComplex: aString ]
 ]
 
 { #category : '*mustache-core' }