diff --git a/ewoksppf/bindings.py b/ewoksppf/bindings.py
index f26dae757e2b362534a6cbbeb8f9aafbbdd83b00..1db4025cf4024d2d1797b69af5de66642658719b 100644
--- a/ewoksppf/bindings.py
+++ b/ewoksppf/bindings.py
@@ -15,6 +15,7 @@ from pypushflow.persistence import register_actorinfo_filter
 
 from . import ppfrunscript
 from ewokscore import load_graph
+from ewokscore import ppftasks
 from ewokscore.variable import value_from_transfer
 from ewokscore.inittask import task_executable
 from ewokscore.inittask import get_varinfo
@@ -46,7 +47,7 @@ def is_ppfmethod(node_attrs: dict) -> bool:
 
 
 def actordata_filter(actorData: dict) -> dict:
-    skip = (ppfrunscript.INFOKEY, "ppfdict")
+    skip = (ppfrunscript.INFOKEY, ppftasks.PPF_DICT_ARGUMENT)
     for key in ["inData", "outData"]:
         data = actorData.get(key, None)
         if data is None:
@@ -57,8 +58,10 @@ def actordata_filter(actorData: dict) -> dict:
             for k, v in data.items()
             if k not in skip
         }
-        if "ppfdict" in data:
-            ppfdict = value_from_transfer(data["ppfdict"], varinfo=varinfo)
+        if ppftasks.PPF_DICT_ARGUMENT in data:
+            ppfdict = value_from_transfer(
+                data[ppftasks.PPF_DICT_ARGUMENT], varinfo=varinfo
+            )
             if ppfdict:
                 actorData[key].update(ppfdict)
     return actorData
@@ -97,7 +100,7 @@ class DecodeRouterActor(RouterActor):
 
     def _extractValue(self, inData):
         if self.is_ppfmethod:
-            value = inData["ppfdict"]
+            value = inData[ppftasks.PPF_DICT_ARGUMENT]
         else:
             if self.itemName in inData:
                 value = inData[self.itemName]
diff --git a/ewoksppf/tests/test_ppf_workflow1.py b/ewoksppf/tests/test_ppf_workflow1.py
index b6f97f3958dd7f2b9af4f90180ddc973d2ff4136..ed46f6688e2291b65fe8f9fe728732868809f5d1 100644
--- a/ewoksppf/tests/test_ppf_workflow1.py
+++ b/ewoksppf/tests/test_ppf_workflow1.py
@@ -21,7 +21,7 @@ def workflow1():
     }
 
     expected_results = {
-        "Python Actor Test": {"ppfdict": {"name": "myname", "reply": "Hello myname!"}}
+        "Python Actor Test": {"_ppfdict": {"name": "myname", "reply": "Hello myname!"}}
     }
 
     return graph, expected_results
diff --git a/ewoksppf/tests/test_ppf_workflow10.py b/ewoksppf/tests/test_ppf_workflow10.py
index 7fff851ee60c0db0e44009c51e49a21df43b4caf..b3be4c234c99f9ce4905aa266c7e3c6c22867951 100644
--- a/ewoksppf/tests/test_ppf_workflow10.py
+++ b/ewoksppf/tests/test_ppf_workflow10.py
@@ -43,7 +43,7 @@ def workflow10(inputs):
 
     limit = inputs["limit"]
     expected_result = {
-        "ppfdict": {"doContinue": "false", "limit": limit, "value": limit}
+        "_ppfdict": {"doContinue": "false", "limit": limit, "value": limit}
     }
 
     return graph, expected_result
diff --git a/ewoksppf/tests/test_ppf_workflow11.py b/ewoksppf/tests/test_ppf_workflow11.py
index f4c4ad41e214653afff7e2f89ffb8876bc57ab5a..9da959ee420571a418ac7f8d43e4181f109798ae 100644
--- a/ewoksppf/tests/test_ppf_workflow11.py
+++ b/ewoksppf/tests/test_ppf_workflow11.py
@@ -114,16 +114,16 @@ def workflow11():
     }
 
     expected_results = {
-        "addtask1": {"ppfdict": {"value": 2}},
-        ("submodel11b", "in11b"): {"ppfdict": {"value": 2}},
-        ("submodel11b", "addtask2ba"): {"ppfdict": {"value": 3}},
-        ("submodel11b", ("submodel11a", "in11a")): {"ppfdict": {"value": 3}},
-        ("submodel11b", ("submodel11a", "addtask2aa")): {"ppfdict": {"value": 4}},
-        ("submodel11b", ("submodel11a", "addtask2ab")): {"ppfdict": {"value": 5}},
-        ("submodel11b", ("submodel11a", "out11a")): {"ppfdict": {"value": 5}},
-        ("submodel11b", "addtask2bb"): {"ppfdict": {"value": 6}},
-        ("submodel11b", "out11b"): {"ppfdict": {"value": 6}},
-        "addtask3": {"ppfdict": {"value": 7}},
+        "addtask1": {"_ppfdict": {"value": 2}},
+        ("submodel11b", "in11b"): {"_ppfdict": {"value": 2}},
+        ("submodel11b", "addtask2ba"): {"_ppfdict": {"value": 3}},
+        ("submodel11b", ("submodel11a", "in11a")): {"_ppfdict": {"value": 3}},
+        ("submodel11b", ("submodel11a", "addtask2aa")): {"_ppfdict": {"value": 4}},
+        ("submodel11b", ("submodel11a", "addtask2ab")): {"_ppfdict": {"value": 5}},
+        ("submodel11b", ("submodel11a", "out11a")): {"_ppfdict": {"value": 5}},
+        ("submodel11b", "addtask2bb"): {"_ppfdict": {"value": 6}},
+        ("submodel11b", "out11b"): {"_ppfdict": {"value": 6}},
+        "addtask3": {"_ppfdict": {"value": 7}},
     }
 
     return graph, expected_results
diff --git a/ewoksppf/tests/test_ppf_workflow12.py b/ewoksppf/tests/test_ppf_workflow12.py
index a3459de46b2544b7d50391a7cb0e60c91710f0a6..261b94a1a18e79162ae79471c198b7099ad03d5d 100644
--- a/ewoksppf/tests/test_ppf_workflow12.py
+++ b/ewoksppf/tests/test_ppf_workflow12.py
@@ -76,16 +76,16 @@ def workflow12(startvalue, withsubmodel_startvalue):
 
     value = startvalue
     value += 1
-    expected_results = {"addtask1": {"ppfdict": {"value": value}}}
+    expected_results = {"addtask1": {"_ppfdict": {"value": value}}}
     if startvalue == withsubmodel_startvalue:
-        expected_results[("submodel12", "in")] = {"ppfdict": {"value": value}}
+        expected_results[("submodel12", "in")] = {"_ppfdict": {"value": value}}
         value += 1
-        expected_results[("submodel12", "addtask2a")] = {"ppfdict": {"value": value}}
+        expected_results[("submodel12", "addtask2a")] = {"_ppfdict": {"value": value}}
         value += 1
-        expected_results[("submodel12", "addtask2b")] = {"ppfdict": {"value": value}}
-        expected_results[("submodel12", "out")] = {"ppfdict": {"value": value}}
+        expected_results[("submodel12", "addtask2b")] = {"_ppfdict": {"value": value}}
+        expected_results[("submodel12", "out")] = {"_ppfdict": {"value": value}}
         value += 1
-        expected_results["addtask2"] = {"ppfdict": {"value": value}}
+        expected_results["addtask2"] = {"_ppfdict": {"value": value}}
 
     return graph, expected_results
 
diff --git a/ewoksppf/tests/test_ppf_workflow13.py b/ewoksppf/tests/test_ppf_workflow13.py
index 63dd8a11197e10bd0071720c42e44e0579b42c5e..1f88da1280576dffc0fba73caf7b85876ccee6cf 100644
--- a/ewoksppf/tests/test_ppf_workflow13.py
+++ b/ewoksppf/tests/test_ppf_workflow13.py
@@ -75,14 +75,14 @@ def workflow13(startvalue, withlastnode_startvalue):
     }
 
     expected_results = {
-        "addtask1": {"ppfdict": {"value": startvalue + 1}},
-        ("submodel13", "in"): {"ppfdict": {"value": startvalue + 1}},
-        ("submodel13", "addtask2a"): {"ppfdict": {"value": startvalue + 2}},
-        ("submodel13", "addtask2b"): {"ppfdict": {"value": startvalue + 3}},
-        ("submodel13", "out"): {"ppfdict": {"value": startvalue + 3}},
+        "addtask1": {"_ppfdict": {"value": startvalue + 1}},
+        ("submodel13", "in"): {"_ppfdict": {"value": startvalue + 1}},
+        ("submodel13", "addtask2a"): {"_ppfdict": {"value": startvalue + 2}},
+        ("submodel13", "addtask2b"): {"_ppfdict": {"value": startvalue + 3}},
+        ("submodel13", "out"): {"_ppfdict": {"value": startvalue + 3}},
     }
     if startvalue == withlastnode_startvalue:
-        expected_results["addtask2"] = {"ppfdict": {"value": startvalue + 4}}
+        expected_results["addtask2"] = {"_ppfdict": {"value": startvalue + 4}}
 
     return graph, expected_results
 
diff --git a/ewoksppf/tests/test_ppf_workflow14.py b/ewoksppf/tests/test_ppf_workflow14.py
index 8ddf3c8b2ae2c96068cfda7cf4ad3e9dea2d9111..241d12f8090aeb07300e9b1e1ef36898216d9182 100644
--- a/ewoksppf/tests/test_ppf_workflow14.py
+++ b/ewoksppf/tests/test_ppf_workflow14.py
@@ -102,14 +102,14 @@ def workflow14():
     }
 
     expected_results = {
-        "addtask1": {"ppfdict": {"value": 2}},
-        ("submodel14b", "In"): {"ppfdict": {"value": 2}},
-        ("submodel14b", ("submodel14a", "In")): {"ppfdict": {"value": 2}},
-        ("submodel14b", ("submodel14a", "addtask2aa")): {"ppfdict": {"value": 3}},
-        ("submodel14b", ("submodel14a", "addtask2ab")): {"ppfdict": {"value": 4}},
-        ("submodel14b", ("submodel14a", "Out")): {"ppfdict": {"value": 4}},
-        ("submodel14b", "Out"): {"ppfdict": {"value": 4}},
-        "addtask3": {"ppfdict": {"value": 5}},
+        "addtask1": {"_ppfdict": {"value": 2}},
+        ("submodel14b", "In"): {"_ppfdict": {"value": 2}},
+        ("submodel14b", ("submodel14a", "In")): {"_ppfdict": {"value": 2}},
+        ("submodel14b", ("submodel14a", "addtask2aa")): {"_ppfdict": {"value": 3}},
+        ("submodel14b", ("submodel14a", "addtask2ab")): {"_ppfdict": {"value": 4}},
+        ("submodel14b", ("submodel14a", "Out")): {"_ppfdict": {"value": 4}},
+        ("submodel14b", "Out"): {"_ppfdict": {"value": 4}},
+        "addtask3": {"_ppfdict": {"value": 5}},
     }
 
     return graph, expected_results
diff --git a/ewoksppf/tests/test_ppf_workflow15.py b/ewoksppf/tests/test_ppf_workflow15.py
index 8e53d18eda120b8de3d705276014872ab7f00d6b..dff4bdf9de1dd65290bb3d14dfe3d86cc84b0083 100644
--- a/ewoksppf/tests/test_ppf_workflow15.py
+++ b/ewoksppf/tests/test_ppf_workflow15.py
@@ -87,16 +87,16 @@ def workflow15():
     }
 
     expected_results = {
-        "addtask1": {"ppfdict": {"value": 2}},
-        ("submodel15a", "in"): {"ppfdict": {"value": 2}},
-        ("submodel15a", "addtask1"): {"ppfdict": {"value": 3}},
-        ("submodel15a", "addtask2"): {"ppfdict": {"value": 4}},
-        ("submodel15a", "out"): {"ppfdict": {"value": 4}},
-        ("submodel15b", "in"): {"ppfdict": {"value": 4}},
-        ("submodel15b", "addtask1"): {"ppfdict": {"value": 5}},
-        ("submodel15b", "addtask2"): {"ppfdict": {"value": 6}},
-        ("submodel15b", "out"): {"ppfdict": {"value": 6}},
-        "addtask2": {"ppfdict": {"value": 7}},
+        "addtask1": {"_ppfdict": {"value": 2}},
+        ("submodel15a", "in"): {"_ppfdict": {"value": 2}},
+        ("submodel15a", "addtask1"): {"_ppfdict": {"value": 3}},
+        ("submodel15a", "addtask2"): {"_ppfdict": {"value": 4}},
+        ("submodel15a", "out"): {"_ppfdict": {"value": 4}},
+        ("submodel15b", "in"): {"_ppfdict": {"value": 4}},
+        ("submodel15b", "addtask1"): {"_ppfdict": {"value": 5}},
+        ("submodel15b", "addtask2"): {"_ppfdict": {"value": 6}},
+        ("submodel15b", "out"): {"_ppfdict": {"value": 6}},
+        "addtask2": {"_ppfdict": {"value": 7}},
     }
 
     return graph, expected_results
diff --git a/ewoksppf/tests/test_ppf_workflow16.py b/ewoksppf/tests/test_ppf_workflow16.py
index 2b93ab825e7a74049cbbf1557c606d94c7ce392b..dd89ed9c2ecfb05385043553bc19eff971786183 100644
--- a/ewoksppf/tests/test_ppf_workflow16.py
+++ b/ewoksppf/tests/test_ppf_workflow16.py
@@ -114,18 +114,18 @@ def workflow16():
     }
 
     expected_results = {
-        "addtask1": {"ppfdict": {"value": 2}},
-        ("submodel16b", "in"): {"ppfdict": {"value": 2}},
-        ("submodel16b", "addtask1"): {"ppfdict": {"value": 3}},
-        ("submodel16b", ("submodel16a", "in")): {"ppfdict": {"value": 3}},
-        ("submodel16b", ("submodel16a", "addtask1")): {"ppfdict": {"value": 4}},
-        ("submodel16b", ("submodel16a", "addtask2")): {"ppfdict": {"value": 5}},
+        "addtask1": {"_ppfdict": {"value": 2}},
+        ("submodel16b", "in"): {"_ppfdict": {"value": 2}},
+        ("submodel16b", "addtask1"): {"_ppfdict": {"value": 3}},
+        ("submodel16b", ("submodel16a", "in")): {"_ppfdict": {"value": 3}},
+        ("submodel16b", ("submodel16a", "addtask1")): {"_ppfdict": {"value": 4}},
+        ("submodel16b", ("submodel16a", "addtask2")): {"_ppfdict": {"value": 5}},
         ("submodel16b", ("submodel16a", "out")): {
-            "ppfdict": {"value": 5}
+            "_ppfdict": {"value": 5}
         },  # 2 destinations
-        ("submodel16b", "addtask2"): {"ppfdict": {"value": 6}},
-        ("submodel16b", "out"): {"ppfdict": {"value": 6}},
-        "addtask2": {"ppfdict": {"value": 6}},
+        ("submodel16b", "addtask2"): {"_ppfdict": {"value": 6}},
+        ("submodel16b", "out"): {"_ppfdict": {"value": 6}},
+        "addtask2": {"_ppfdict": {"value": 6}},
     }
 
     return graph, expected_results
diff --git a/ewoksppf/tests/test_ppf_workflow17.py b/ewoksppf/tests/test_ppf_workflow17.py
index d40ee6edf9eb9daa28b266d3992ad414ac594100..9a0a2b77ab28f0d169864ed63a001e633e854790 100644
--- a/ewoksppf/tests/test_ppf_workflow17.py
+++ b/ewoksppf/tests/test_ppf_workflow17.py
@@ -41,7 +41,7 @@ def workflow17(doloop=True):
         "nodes": nodes,
     }
 
-    expected_result = {"ppfdict": {"value": result}}
+    expected_result = {"_ppfdict": {"value": result}}
 
     return graph, expected_result
 
diff --git a/ewoksppf/tests/test_ppf_workflow18.py b/ewoksppf/tests/test_ppf_workflow18.py
index a93e0eb469897037f72bf9fa02697ba6586282f0..fc42e98a770193713b2d743a20d8386082c2de8a 100644
--- a/ewoksppf/tests/test_ppf_workflow18.py
+++ b/ewoksppf/tests/test_ppf_workflow18.py
@@ -38,13 +38,13 @@ def workflow18(dotask4=True):
     }
 
     expected_results = {
-        "task1": {"ppfdict": {"value": 1}},
-        "task2": {"ppfdict": {"value": 11}},
-        "task3": {"ppfdict": {"value": 2}},
+        "task1": {"_ppfdict": {"value": 1}},
+        "task2": {"_ppfdict": {"value": 11}},
+        "task3": {"_ppfdict": {"value": 2}},
     }
 
     if dotask4:
-        expected_results["task4"] = {"ppfdict": {"value": 12}}
+        expected_results["task4"] = {"_ppfdict": {"value": 12}}
     else:
         expected_results["task4"] = None
 
diff --git a/ewoksppf/tests/test_ppf_workflow19.py b/ewoksppf/tests/test_ppf_workflow19.py
index 06f2af8cd01e2c59063fc1d35bdc212201db6dbb..340e43231bdf1c73038abee0af7edd82c24f9542 100644
--- a/ewoksppf/tests/test_ppf_workflow19.py
+++ b/ewoksppf/tests/test_ppf_workflow19.py
@@ -62,7 +62,7 @@ def workflow19():
         "nodes": nodes,
     }
     expected_results = {
-        "ppfdict": {"a": 18, "b": 1, "c": 4, "d": 18, "increment_value": 1}
+        "_ppfdict": {"a": 18, "b": 1, "c": 4, "d": 18, "increment_value": 1}
     }
 
     return graph, expected_results
diff --git a/ewoksppf/tests/test_ppf_workflow20.py b/ewoksppf/tests/test_ppf_workflow20.py
index f37d4ef6ce4535a6a9e2aea6419cfb089d618a11..3d168cfd917fb89b6e56ca4b4f0da114167a1850 100644
--- a/ewoksppf/tests/test_ppf_workflow20.py
+++ b/ewoksppf/tests/test_ppf_workflow20.py
@@ -27,4 +27,4 @@ def test_workflow20(persist, ppf_logging, tmpdir):
         varinfo = None
     graph = workflow20()
     result = execute_graph(graph, inputs={"value": 5}, varinfo=varinfo)
-    assert result["ppfdict"]["value"] == 7
+    assert result["_ppfdict"]["value"] == 7
diff --git a/ewoksppf/tests/test_ppf_workflow3.py b/ewoksppf/tests/test_ppf_workflow3.py
index ed4b02e97552cf0e69c5f91e3087d0c41451d20d..e51bc6aa3e4163384d795cd36a07eb8fd0c6d86f 100644
--- a/ewoksppf/tests/test_ppf_workflow3.py
+++ b/ewoksppf/tests/test_ppf_workflow3.py
@@ -63,9 +63,11 @@ def workflow3():
     }
 
     expected_results = {
-        "first": {"ppfdict": {"name": "first", "reply": "Hello first!"}},
-        ("middle", "mytask"): {"ppfdict": {"name": "middle", "reply": "Hello middle!"}},
-        "last": {"ppfdict": {"name": "last", "reply": "Hello last!"}},
+        "first": {"_ppfdict": {"name": "first", "reply": "Hello first!"}},
+        ("middle", "mytask"): {
+            "_ppfdict": {"name": "middle", "reply": "Hello middle!"}
+        },
+        "last": {"_ppfdict": {"name": "last", "reply": "Hello last!"}},
     }
 
     return graph, expected_results
diff --git a/ewoksppf/tests/test_ppf_workflow6.py b/ewoksppf/tests/test_ppf_workflow6.py
index b0a2660105559f5639324cca9067f7a3d1ddd3cb..419638781018b81eb70823b97e58ea853326c5f0 100644
--- a/ewoksppf/tests/test_ppf_workflow6.py
+++ b/ewoksppf/tests/test_ppf_workflow6.py
@@ -71,12 +71,12 @@ def workflow6():
     }
 
     expected_results = {
-        "addtask1": {"ppfdict": {"value": 2}},
-        ("submodel6", "in"): {"ppfdict": {"value": 2}},
-        ("submodel6", "addtask2a"): {"ppfdict": {"value": 3}},
-        ("submodel6", "addtask2b"): {"ppfdict": {"value": 4}},
-        ("submodel6", "out"): {"ppfdict": {"value": 4}},
-        "addtask3": {"ppfdict": {"value": 5}},
+        "addtask1": {"_ppfdict": {"value": 2}},
+        ("submodel6", "in"): {"_ppfdict": {"value": 2}},
+        ("submodel6", "addtask2a"): {"_ppfdict": {"value": 3}},
+        ("submodel6", "addtask2b"): {"_ppfdict": {"value": 4}},
+        ("submodel6", "out"): {"_ppfdict": {"value": 4}},
+        "addtask3": {"_ppfdict": {"value": 5}},
     }
 
     return graph, expected_results
diff --git a/ewoksppf/tests/test_ppf_workflow7.py b/ewoksppf/tests/test_ppf_workflow7.py
index 8bc0efc3ffcd628b774b7af57ef69ca268cd67bb..86b987eb7d4d8234c33ddef10c41ab087d50ddcd 100644
--- a/ewoksppf/tests/test_ppf_workflow7.py
+++ b/ewoksppf/tests/test_ppf_workflow7.py
@@ -60,9 +60,9 @@ def workflow7():
     }
 
     expected_results = {
-        "addtask1": {"ppfdict": {"all_arguments": {"value": 2}}},
-        ("submodel7", "addtask2"): {"ppfdict": {"all_arguments": {"value": 3}}},
-        "addtask3": {"ppfdict": {"all_arguments": {"value": 4}}},
+        "addtask1": {"_ppfdict": {"all_arguments": {"value": 2}}},
+        ("submodel7", "addtask2"): {"_ppfdict": {"all_arguments": {"value": 3}}},
+        "addtask3": {"_ppfdict": {"all_arguments": {"value": 4}}},
     }
 
     return graph, expected_results
diff --git a/ewoksppf/tests/test_ppf_workflow8.py b/ewoksppf/tests/test_ppf_workflow8.py
index e43a9240d20847b831072a729141d39b7436079b..f116bc13e9a3261056d6cef7ffe7b9a5dab7ac91 100644
--- a/ewoksppf/tests/test_ppf_workflow8.py
+++ b/ewoksppf/tests/test_ppf_workflow8.py
@@ -60,9 +60,9 @@ def workflow8():
     }
 
     expected_results = {
-        "addtask1": {"ppfdict": {"a": 1, "b": 2}},
-        ("submodel8", "addtask2"): {"ppfdict": {"a": 1, "b": 2, "c": 3}},
-        "addtask3": {"ppfdict": {"a": 1, "b": 2, "c": 3, "d": 6}},
+        "addtask1": {"_ppfdict": {"a": 1, "b": 2}},
+        ("submodel8", "addtask2"): {"_ppfdict": {"a": 1, "b": 2, "c": 3}},
+        "addtask3": {"_ppfdict": {"a": 1, "b": 2, "c": 3, "d": 6}},
     }
 
     return graph, expected_results
diff --git a/ewoksppf/tests/test_ppf_workflow9.py b/ewoksppf/tests/test_ppf_workflow9.py
index c2057c49d14bd769985e0e10dd7239383ead395f..9020d9d088f6b5eb772b57b9906ccf89404e58b6 100644
--- a/ewoksppf/tests/test_ppf_workflow9.py
+++ b/ewoksppf/tests/test_ppf_workflow9.py
@@ -47,9 +47,9 @@ def workflow9():
     # the same task instance as addtask2 (same task hash). So it
     # will appear as "done" and have a result.
     expected_results = {
-        "addtask1": {"ppfdict": {"value": 2}},
-        "addtask2": {"ppfdict": {"value": 3}},
-        "addtask3": {"ppfdict": {"value": 3}},
+        "addtask1": {"_ppfdict": {"value": 2}},
+        "addtask2": {"_ppfdict": {"value": 3}},
+        "addtask3": {"_ppfdict": {"value": 3}},
     }
 
     return graph, expected_results