diff --git a/src/gen_cpp_Engine.ysl2 b/src/gen_cpp_Engine.ysl2
index 4f5e50c..5133e65 100644
--- a/src/gen_cpp_Engine.ysl2
+++ b/src/gen_cpp_Engine.ysl2
@@ -28,11 +28,11 @@ tstylesheet {
 
     template "method" {
         const "mangled" call "mangle";
-        const "returning", "count(parm/creates|parm/returns)";
+        const "returning", "count(parm/creates|parm/returns|parm/inout)";
         const "CretType" choose {
             when "$returning = 0" > void
             when "$returning = 1" 
-                call "jni_type" with "type", "name(parm[returns|creates]/*[2])";
+                call "jni_type" with "type", "name(parm[returns|creates|inout]/*[2])";
             when "$returning > 0" > jobject
         }
         const "CretDefault" choose {
@@ -43,14 +43,14 @@ tstylesheet {
         ||
         JNIEXPORT «$CretType» JNICALL «$mangled»(
                 JNIEnv *env,
-                jobject obj`apply "parm[in]", mode=sig`
+                jobject obj`apply "parm[in|inout]", mode=sig`
             )
         {
             PEP_SESSION session = (PEP_SESSION) callLongMethod(env, obj, "getHandle");
 
         ||
 
-        apply "parm[in]", mode=in;
+        apply "parm[in|inout]", mode=in;
         apply "parm[creates|returns]", mode=out;
         ||
 
@@ -64,7 +64,7 @@ tstylesheet {
 
         ||
 
-        apply "parm[returns|creates]", mode=return;
+        apply "parm[returns|creates|inout]", mode=return;
 
         choose {
             when "$returning > 1" {
@@ -78,7 +78,7 @@ tstylesheet {
                     result_ = env->NewObject(clazz_result_, constructor_result_, obj);
                 ||
 
-                apply "parm[returns|creates]", mode=setresult
+                apply "parm[returns|creates|inout]", mode=setresult
                     with "jtype" > org/pEp/jniadapter/Engine$_«@name»_Return
 
                 ||
@@ -89,7 +89,7 @@ tstylesheet {
             when "$returning = 1" {
 
                 ||
-                    return «name(parm[returns|creates]/*[3])»_;
+                    return «name(parm[returns|creates|inout]/*[3])»_;
                 ||
             }
         }
diff --git a/src/gen_java_Engine.ysl2 b/src/gen_java_Engine.ysl2
index 19ac6bc..7abce73 100644
--- a/src/gen_java_Engine.ysl2
+++ b/src/gen_java_Engine.ysl2
@@ -137,21 +137,21 @@ tstylesheet {
 
     template "method", mode=plain {
         const "convert", "count(parm/stringlist|parm/stringpairlist|parm/string|parm/identity|parm/identitylist) > 0";
-        const "singlereturn", "count(parm/creates|parm/returns) = 1";
-        const "multireturn", "count(parm/creates|parm/returns) > 1";
+        const "singlereturn", "count(parm/creates|parm/returns|parms/inout) = 1";
+        const "multireturn", "count(parm/creates|parm/returns|parms/inout) > 1";
 
         if "$multireturn" {
             if "$convert"
             ||
             private class _«@name»_Return {
-            `` apply "parm[creates|returns]", 1, mode=intermediate with "public", 1;
+            `` apply "parm[creates|returns|inout]", 1, mode=intermediate with "public", 1;
             }
 
             ||
 
             ||
             public class «@name»_Return {
-            `` apply "parm[creates|returns]", 1, mode=java with "public", 1;
+            `` apply "parm[creates|returns|inout]", 1, mode=java with "public", 1;
             }
 
             ||
@@ -160,14 +160,14 @@ tstylesheet {
         if "$convert"
         ||
         private native `call "returnInter"` _«@name»(
-        `` apply "parm[in]", 2, mode=intermediate
+        `` apply "parm[in|inout]", 2, mode=intermediate
             ) throws pEpException;
 
         ||
 
         ||
         public `if "not($convert)" > native ``call "returnJava"` «@name»(
-        `` apply "parm[in]", 2, mode=java
+        `` apply "parm[in|inout]", 2, mode=java
             ) throws pEpException`if "not($convert)" > ;`
         ||
 
@@ -212,9 +212,9 @@ tstylesheet {
 
             if "$multireturn"
             ||
-                _«@name»_Return _result = _«@name»(`apply "parm[in]", mode=call;`);
+                _«@name»_Return _result = _«@name»(`apply "parm[in|inout]", mode=call;`);
                 «@name»_Return result = new «@name»_Return();
-                `` apply "parm[creates|returns]", mode=convertOut;
+                `` apply "parm[creates|returns|inout]", mode=convertOut;
                 return result;
             ||
 
@@ -272,7 +272,7 @@ tstylesheet {
         const "type", "name(*[2])";
         const "name" call "lcase" with "text", "name(*[3])";
 
-        if "$dir = 'in'" choose {
+        if "$dir = 'in' or $dir = 'inout'" choose {
             when "$type = 'string' or $type = 'stringlist'"
                 | ¡$type _«$name» = AbstractEngine.toUTF8(«$name»);
             when "$type = 'identity'"
diff --git a/src/pEp.yml2 b/src/pEp.yml2
index a3f94e1..ac6a8f9 100644
--- a/src/pEp.yml2
+++ b/src/pEp.yml2
@@ -170,7 +170,7 @@ namespace pEp {
             );
 
         method decrypt_message(
-                in message src,
+                inout message src,
                 creates message dst,
                 creates stringlist keylist,
                 returns Rating rating,