diff --git a/draft/library/wsf_js_widget/kernel/webcontrol/wsf_json_object.e b/draft/library/wsf_js_widget/kernel/webcontrol/wsf_json_object.e
index a42e114e..c125181c 100644
--- a/draft/library/wsf_js_widget/kernel/webcontrol/wsf_json_object.e
+++ b/draft/library/wsf_js_widget/kernel/webcontrol/wsf_json_object.e
@@ -16,114 +16,133 @@ create
 
 feature
 
-	put_string (value: READABLE_STRING_GENERAL; key: JSON_STRING)
+	put_string (value: detachable READABLE_STRING_GENERAL; key: JSON_STRING)
 			-- Assuming there is no item of key `key',
 			-- insert `value' with `key'.
 		require
 			key_not_present: not has_key (key)
 		local
-			l_value: JSON_STRING
+			l_value: detachable JSON_STRING
 		do
-			create l_value.make_json_from_string_32 (value.as_string_32)
+			if attached value as a_value then
+				create l_value.make_json_from_string_32 (a_value.as_string_32)
+			end
 			put (l_value, key)
 		end
 
-	put_integer (value: INTEGER_64; key: JSON_STRING)
+	put_integer (value: detachable INTEGER_64; key: JSON_STRING)
 			-- Assuming there is no item of key `key',
 			-- insert `value' with `key'.
 		require
 			key_not_present: not has_key (key)
 		local
-			l_value: JSON_NUMBER
+			l_value: detachable JSON_NUMBER
 		do
-			create l_value.make_integer (value)
+			if attached value as a_value then
+				create l_value.make_integer (a_value)
+			end
 			put (l_value, key)
 		end
 
-	put_natural (value: NATURAL_64; key: JSON_STRING)
+	put_natural (value: detachable NATURAL_64; key: JSON_STRING)
 			-- Assuming there is no item of key `key',
 			-- insert `value' with `key'.
 		require
 			key_not_present: not has_key (key)
 		local
-			l_value: JSON_NUMBER
+			l_value: detachable JSON_NUMBER
 		do
-			create l_value.make_natural (value)
+			if attached value as a_value then
+				create l_value.make_natural (a_value)
+			end
 			put (l_value, key)
 		end
 
-	put_real (value: DOUBLE; key: JSON_STRING)
+	put_real (value: detachable DOUBLE; key: JSON_STRING)
 			-- Assuming there is no item of key `key',
 			-- insert `value' with `key'.
 		require
 			key_not_present: not has_key (key)
 		local
-			l_value: JSON_NUMBER
+			l_value: detachable JSON_NUMBER
 		do
-			create l_value.make_real (value)
+			if attached value as a_value then
+				create l_value.make_real (a_value)
+			end
 			put (l_value, key)
 		end
 
-	put_boolean (value: BOOLEAN; key: JSON_STRING)
+	put_boolean (value: detachable BOOLEAN; key: JSON_STRING)
 			-- Assuming there is no item of key `key',
 			-- insert `value' with `key'.
 		require
 			key_not_present: not has_key (key)
 		local
-			l_value: JSON_BOOLEAN
+			l_value: detachable JSON_BOOLEAN
 		do
-			create l_value.make_boolean (value)
+			if attached value as a_value then
+				create l_value.make_boolean (a_value)
+			end
 			put (l_value, key)
 		end
 
-	replace_with_string (value: READABLE_STRING_GENERAL; key: JSON_STRING)
+	replace_with_string (value: detachable READABLE_STRING_GENERAL; key: JSON_STRING)
 			-- Assuming there is no item of key `key',
 			-- insert `value' with `key'.
 		local
-			l_value: JSON_STRING
+			l_value: detachable JSON_STRING
 		do
-			create l_value.make_json_from_string_32 (value.as_string_32)
+			if attached value as a_value then
+				create l_value.make_json_from_string_32 (value.as_string_32)
+			end
 			replace (l_value, key)
 		end
 
-	replace_with_integer (value: INTEGER_64; key: JSON_STRING)
+	replace_with_integer (value: detachable INTEGER_64; key: JSON_STRING)
 			-- Assuming there is no item of key `key',
 			-- insert `value' with `key'.
 		local
-			l_value: JSON_NUMBER
+			l_value: detachable JSON_NUMBER
 		do
-			create l_value.make_integer (value)
+			if attached value as a_value then
+				create l_value.make_integer (a_value)
+			end
 			replace (l_value, key)
 		end
 
-	replace_with_with_natural (value: NATURAL_64; key: JSON_STRING)
+	replace_with_with_natural (value: detachable NATURAL_64; key: JSON_STRING)
 			-- Assuming there is no item of key `key',
 			-- insert `value' with `key'.
 		local
-			l_value: JSON_NUMBER
+			l_value: detachable JSON_NUMBER
 		do
-			create l_value.make_natural (value)
+			if attached value as a_value then
+				create l_value.make_natural (a_value)
+			end
 			replace (l_value, key)
 		end
 
-	replace_with_real (value: DOUBLE; key: JSON_STRING)
+	replace_with_real (value: detachable DOUBLE; key: JSON_STRING)
 			-- Assuming there is no item of key `key',
-			-- insert `value' with `key'.
+			-- insert `value' with `key'
 		local
-			l_value: JSON_NUMBER
+			l_value: detachable JSON_NUMBER
 		do
-			create l_value.make_real (value)
+			if attached value as a_value then
+				create l_value.make_real (a_value)
+			end
 			replace (l_value, key)
 		end
 
-
-	replace_with_boolean (value: BOOLEAN; key: JSON_STRING)
+	replace_with_boolean (value: detachable BOOLEAN; key: JSON_STRING)
 			-- Assuming there is no item of key `key',
 			-- insert `value' with `key'.
 		local
-			l_value: JSON_BOOLEAN
+			l_value: detachable JSON_BOOLEAN
 		do
-			create l_value.make_boolean (value)
+			if attached value as a_value then
+				create l_value.make_boolean (a_value)
+			end
 			replace (l_value, key)
 		end