diff --git a/src/UnifiedFFI/BlockClosure.extension.st b/src/UnifiedFFI/BlockClosure.extension.st
new file mode 100644
index 00000000000..36dd5708d87
--- /dev/null
+++ b/src/UnifiedFFI/BlockClosure.extension.st
@@ -0,0 +1,35 @@
+Extension { #name : #BlockClosure }
+
+{ #category : #'*UnifiedFFI' }
+BlockClosure >> on: exception fork: handlerAction return: answerAction [
+	"This is the same as #on:fork: but instead just fork and letting the flow continues, in 
+	 case of an error it also evaluates answerAction and returns its result."
+		
+	^ self on: exception do: [:ex |
+		| onDoCtx handler bottom thisCtx |
+		
+		onDoCtx := thisContext.
+		thisCtx := onDoCtx home.
+
+		"find the context on stack for which this method's is sender"
+
+		[ onDoCtx sender == thisCtx] whileFalse: [ 
+			onDoCtx := onDoCtx sender.
+			onDoCtx ifNil: [ 
+				"Can't find our home context. seems like we're already forked
+				and handling another exception in new thread. In this case, just pass it through handler."
+				^ handlerAction cull: ex ] ].
+
+		bottom := [ Processor terminateActive ] asContext.
+		onDoCtx privSender: bottom.
+
+		handler := [ handlerAction cull: ex ] asContext.
+		handler privSender: thisContext sender.
+
+		(Process forContext: handler priority: Processor activePriority) resume.
+
+		"cut the stack of current process"
+		thisContext privSender: thisCtx.
+		answerAction cull: exception ]
+
+]
diff --git a/src/UnifiedFFI/FFIBool.class.st b/src/UnifiedFFI/FFIBool.class.st
index 8ece0daf33e..4d4cb176384 100644
--- a/src/UnifiedFFI/FFIBool.class.st
+++ b/src/UnifiedFFI/FFIBool.class.st
@@ -33,6 +33,12 @@ FFIBool >> basicHandle: aHandle at: index put: value [
 	^ aHandle booleanAt: index put: value
 ]
 
+{ #category : #accessing }
+FFIBool >> defaultReturnOnError [
+
+	^ false
+]
+
 { #category : #'stack parameter classification' }
 FFIBool >> stackValueParameterClass [
 	^ #integer
diff --git a/src/UnifiedFFI/FFICallback.class.st b/src/UnifiedFFI/FFICallback.class.st
index 6694a41568a..a6d359b0a0c 100644
--- a/src/UnifiedFFI/FFICallback.class.st
+++ b/src/UnifiedFFI/FFICallback.class.st
@@ -69,7 +69,7 @@ FFICallback class >> signature: aSignature block: aBlock [
 	^ self new signature: aSignature block: aBlock
 ]
 
-{ #category : #'as yet unclassified' }
+{ #category : #evaluation }
 FFICallback >> argumentsFor: stackPointer context: callbackContext [
 	| index architecture intRegisterCount intRegisterSize intRegisterIndex floatRegisterCount floatRegisterSize floatRegisterIndex floatRegisters intRegisters structureRegisterLayout |
 	self flag: 'TODO: Refactor and improve this code.'.
@@ -130,6 +130,15 @@ FFICallback >> argumentsFor: stackPointer context: callbackContext [
 			value ].	
 ]
 
+{ #category : #evaluation }
+FFICallback >> executeWithArguments: argumentValues [
+	
+	^ [ block valueWithArguments: argumentValues ]
+		on: Error 
+		fork: [ :e | e pass ]
+		return: [ self returnOnError ]
+]
+
 { #category : #private }
 FFICallback >> ffiBindingOf: aName [
 	^ self class ffiBindingOf: aName
@@ -153,6 +162,12 @@ FFICallback >> newParser [
 		yourself
 ]
 
+{ #category : #private }
+FFICallback >> returnOnError [
+
+	^ functionSpec returnType defaultReturnOnError
+]
+
 { #category : #initialization }
 FFICallback >> signature: signature "<String>" block: aBlock [ "<BlockClosure>"
 	functionSpec := self newParser parseAnonymousFunction: signature.
@@ -169,12 +184,11 @@ FFICallback >> thunk [
 ]
 
 { #category : #evaluation }
-FFICallback >> valueWithContext: callbackContext sp: stackPointer [ 
+FFICallback >> valueWithContext: callbackContext sp: stackPointer [
 	| argumentValues |
-	
-	self flag: #todo. "This can be optimised in a shadow method"
+
 	argumentValues := self argumentsFor: stackPointer context: callbackContext.
 	^ functionSpec returnType 
 		callbackReturnOn: callbackContext 
-		for: (block valueWithArguments: argumentValues)
+		for: (self executeWithArguments: argumentValues)
 ]
diff --git a/src/UnifiedFFI/FFICharacterType.class.st b/src/UnifiedFFI/FFICharacterType.class.st
index 6c23e6ca19c..20d9bd15b1b 100644
--- a/src/UnifiedFFI/FFICharacterType.class.st
+++ b/src/UnifiedFFI/FFICharacterType.class.st
@@ -33,6 +33,12 @@ FFICharacterType >> basicHandle: aHandle at: index put: value [
 	^ aHandle signedCharAt: index put: value
 ]
 
+{ #category : #acccessing }
+FFICharacterType >> defaultReturnOnError [
+
+	^ Character null
+]
+
 { #category : #testing }
 FFICharacterType >> needsArityPacking [
 	">1 because it can be a 'char *', then just roll when is 'char**' or bigger"
diff --git a/src/UnifiedFFI/FFIExternalReferenceType.class.st b/src/UnifiedFFI/FFIExternalReferenceType.class.st
index 0e94a5920cb..52d1bd71808 100644
--- a/src/UnifiedFFI/FFIExternalReferenceType.class.st
+++ b/src/UnifiedFFI/FFIExternalReferenceType.class.st
@@ -48,6 +48,12 @@ FFIExternalReferenceType >> basicHandle: aHandle at: index put: value [
 
 ]
 
+{ #category : #accessing }
+FFIExternalReferenceType >> defaultReturnOnError [
+
+	^ ExternalAddress null
+]
+
 { #category : #'emitting code' }
 FFIExternalReferenceType >> emitReturn: aBuilder resultTempVar: resultVar context: aContext [
 	^ aBuilder 
diff --git a/src/UnifiedFFI/FFIExternalString.class.st b/src/UnifiedFFI/FFIExternalString.class.st
index 80e1bf91151..82c09b6de5d 100644
--- a/src/UnifiedFFI/FFIExternalString.class.st
+++ b/src/UnifiedFFI/FFIExternalString.class.st
@@ -33,6 +33,12 @@ FFIExternalString >> basicHandle: aHandle at: index put: value [
 	self error: 'Not sure I want to do this.'
 ]
 
+{ #category : #accessing }
+FFIExternalString >> defaultReturnOnError [
+
+	^ ''
+]
+
 { #category : #accessing }
 FFIExternalString >> externalTypeSize [
 	^ self pointerSize "i am live and die as a pointer (a char*)"
diff --git a/src/UnifiedFFI/FFIExternalType.class.st b/src/UnifiedFFI/FFIExternalType.class.st
index 422808565b8..5c872d6450a 100644
--- a/src/UnifiedFFI/FFIExternalType.class.st
+++ b/src/UnifiedFFI/FFIExternalType.class.st
@@ -130,6 +130,17 @@ FFIExternalType >> callbackValueFor: anObject at: index [
 	^ self handle: anObject at: index
 ]
 
+{ #category : #accessing }
+FFIExternalType >> defaultReturnOnError [
+	"In case of a callback error, the image will try to show a debugger and that will most ot the 
+	 time crashes the VM (because it will break the process and will let a C function waiting and 
+	 and in incorrect state). 
+	 To prevent that, we use #on:fork:return: (look for senders) and, while forking the error to 
+	 allow user to debug his error, we also return a 'default' value, that may be also wrong."
+
+	^ self subclassResponsibility
+]
+
 { #category : #'emitting code' }
 FFIExternalType >> emitArgument: aBuilder context: aContext [ 
 	self basicEmitArgument: aBuilder context: aContext.
diff --git a/src/UnifiedFFI/FFIFloatType.class.st b/src/UnifiedFFI/FFIFloatType.class.st
index aef7b8b7629..abe1418cc34 100644
--- a/src/UnifiedFFI/FFIFloatType.class.st
+++ b/src/UnifiedFFI/FFIFloatType.class.st
@@ -12,6 +12,12 @@ FFIFloatType >> callbackReturnOn: callbackContext for: aFloat [
 	^ callbackContext floatResult: aFloat
 ]
 
+{ #category : #accessing }
+FFIFloatType >> defaultReturnOnError [
+
+	^ 0.0
+]
+
 { #category : #'stack parameter classification' }
 FFIFloatType >> stackValueParameterClass [
 	^ #float
diff --git a/src/UnifiedFFI/FFIIntegerType.class.st b/src/UnifiedFFI/FFIIntegerType.class.st
index 8996fa8243c..187299b1857 100644
--- a/src/UnifiedFFI/FFIIntegerType.class.st
+++ b/src/UnifiedFFI/FFIIntegerType.class.st
@@ -7,6 +7,12 @@ Class {
 	#category : #'UnifiedFFI-Types'
 }
 
+{ #category : #accessing }
+FFIIntegerType >> defaultReturnOnError [
+
+	^ 0
+]
+
 { #category : #'stack parameter classification' }
 FFIIntegerType >> stackValueParameterClass [
 	^ #integer
diff --git a/src/UnifiedFFI/FFIVoid.class.st b/src/UnifiedFFI/FFIVoid.class.st
index 18e55ecee92..a399aa135fb 100644
--- a/src/UnifiedFFI/FFIVoid.class.st
+++ b/src/UnifiedFFI/FFIVoid.class.st
@@ -31,6 +31,12 @@ FFIVoid >> callbackReturnOn: callbackContext for: anObject [
 
 ]
 
+{ #category : #accessing }
+FFIVoid >> defaultReturnOnError [
+
+	^ nil
+]
+
 { #category : #'emitting code' }
 FFIVoid >> emitPointerReturn: aBuilder resultTempVar: resultVar context: aContext [
 	^ aBuilder