diff --git a/Compiler/BackEnd/BackendDAEOptimize.mo b/Compiler/BackEnd/BackendDAEOptimize.mo
index 5458ec26c32..b9d1895ab09 100644
--- a/Compiler/BackEnd/BackendDAEOptimize.mo
+++ b/Compiler/BackEnd/BackendDAEOptimize.mo
@@ -110,6 +110,122 @@ algorithm
   outDAE.shared := shared;
 end simplifyAllExpressions;
 
+// =============================================================================
+// simplifyInStream
+//
+// OM introduces $OMC$PosetiveMax which can simplified using min or max attribute
+// see Modelica spec for inStream
+// author: Vitalij Ruge
+// see. #3885, 4441
+// =============================================================================
+
+public function simplifyInStream
+  input output BackendDAE.BackendDAE dae;
+protected
+  BackendDAE.Shared shared = dae.shared;
+  BackendDAE.EqSystems eqs = dae.eqs;
+  list<BackendDAE.Variables> vars = list(eq.orderedVars for eq in eqs);
+algorithm
+  // from the description inputs are part of globalKnownVars and localKnownVars :(
+  vars := shared.globalKnownVars :: vars; // need inputs with min = 0 or max = 0
+  vars := shared.localKnownVars :: vars;
+  _ := BackendDAEUtil.traverseBackendDAEExpsNoCopyWithUpdate(dae, simplifyInStreamWork, vars);
+end simplifyInStream;
+
+
+protected function simplifyInStreamWork
+  input DAE.Exp inExp;
+  input list<BackendDAE.Variables> inVars;
+  output DAE.Exp outExp;
+  output list<BackendDAE.Variables> outVars = inVars;
+algorithm
+  outExp := Expression.traverseExpBottomUp(inExp, simplifyInStreamWork2, outVars);
+end simplifyInStreamWork;
+
+protected function simplifyInStreamWork2
+  input DAE.Exp inExp;
+  input list<BackendDAE.Variables> inVars;
+  output DAE.Exp outExp;
+  output list<BackendDAE.Variables> outVars = inVars;
+algorithm
+  outExp := match(inExp)
+              local DAE.Type tp;
+              DAE.ComponentRef cr;
+              DAE.Exp e, expr;
+              Option<DAE.Exp> eMin;
+              Option<DAE.Exp> eMax;
+              Boolean isZero;
+
+
+            case DAE.CALL(path=Absyn.IDENT("$OMC$PositiveMax"),expLst={e as DAE.CREF(componentRef=cr), expr})
+              algorithm
+               (eMin, eMax) := simplifyInStreamWorkExpresion(cr, outVars);
+               isZero := simplifyInStreamWorkSimplify(eMin, false);
+               tp := ComponentReference.crefTypeFull(cr);
+               then
+                  if isZero then e else Expression.makePureBuiltinCall("max", {e, expr}, tp);
+
+            case DAE.CALL(path=Absyn.IDENT("$OMC$PositiveMax"),expLst={e as DAE.UNARY(DAE.UMINUS(tp), DAE.CREF(componentRef=cr)), expr})
+              algorithm
+               (eMin, eMax) := simplifyInStreamWorkExpresion(cr, outVars);
+               isZero := simplifyInStreamWorkSimplify(eMax, true);
+               then
+                  if isZero then Expression.createZeroExpression(tp) else Expression.makePureBuiltinCall("max", {e, expr}, tp);
+
+            case DAE.CALL(path=Absyn.IDENT("$OMC$PositiveMax"),expLst={e, expr})
+               guard Expression.isZero(e)
+               then e;
+
+            case DAE.CALL(path=Absyn.IDENT("$OMC$PositiveMax"),expLst={e, expr})
+               //algorithm
+                   //print("\nsimplifyInStreamWork: ");
+                   //print(ExpressionDump.printExpStr(inExp));
+                   //print(" <-> ");
+                   //print(ExpressionDump.printExpStr(e));
+
+               then Expression.makePureBuiltinCall("max", {e, expr}, Expression.typeof(e));
+
+            case _
+               then inExp;
+            end match;
+
+end simplifyInStreamWork2;
+
+protected function simplifyInStreamWorkExpresion
+  input DAE.ComponentRef cr;
+  input list<BackendDAE.Variables> inVars;
+  output Option<DAE.Exp> outMin = NONE();
+  output Option<DAE.Exp> outMax = NONE();
+protected
+  BackendDAE.Var v;
+algorithm
+   for vars in inVars loop
+      try
+         (v, _) := BackendVariable.getVarSingle(cr, vars);
+         (outMin, outMax) := BackendVariable.getMinMaxAttribute(v);
+         break;
+      else
+        // search
+      end try;
+   end for;
+
+end simplifyInStreamWorkExpresion;
+
+protected function simplifyInStreamWorkSimplify
+  input Option<DAE.Exp> bound;
+  input Boolean neg;
+  output Boolean isZero;
+algorithm
+   isZero := match bound
+              local Real r;
+            case SOME(DAE.RCONST(r))
+              then if neg then r<= 0.0 else r >= 0.0;
+            case _
+              then false;
+            end match;
+end simplifyInStreamWorkSimplify;
+
+
 // =============================================================================
 // simplify time independent function calls
 //
diff --git a/Compiler/BackEnd/BackendDAEUtil.mo b/Compiler/BackEnd/BackendDAEUtil.mo
index c73a40b1fe7..c748195fc07 100644
--- a/Compiler/BackEnd/BackendDAEUtil.mo
+++ b/Compiler/BackEnd/BackendDAEUtil.mo
@@ -7495,6 +7495,7 @@ public function allPreOptimizationModules
     (BackendDAEOptimize.removeUnusedVariables, "removeUnusedVariables"),
     (BackendDAEOptimize.residualForm, "residualForm"),
     (BackendDAEOptimize.simplifyAllExpressions, "simplifyAllExpressions"),
+    (BackendDAEOptimize.simplifyInStream, "simplifyInStream"),
     (BackendDump.dumpDAE, "dumpDAE"),
     (XMLDump.dumpDAEXML, "dumpDAEXML"),
     // This should indeed be at the end
@@ -7621,6 +7622,10 @@ algorithm
   preOptModules := getPreOptModulesString();
   preOptModules := Util.getOptionOrDefault(inPreOptModules, preOptModules);
 
+  if isSome(getGlobalRoot(Global.isInStream)) then
+     enabledModules := "simplifyInStream"::enabledModules;
+  end if;
+
   if Flags.getConfigBool(Flags.DEFAULT_OPT_MODULES_ORDERING) then
     // handle special flags, which enable modules
 
diff --git a/Compiler/FrontEnd/ConnectUtil.mo b/Compiler/FrontEnd/ConnectUtil.mo
index a0dca169098..c149b19172d 100644
--- a/Compiler/FrontEnd/ConnectUtil.mo
+++ b/Compiler/FrontEnd/ConnectUtil.mo
@@ -74,6 +74,7 @@ import PrefixUtil;
 import System;
 import Types;
 import Util;
+import Global;
 
 // Import some types from Connect.
 import Connect.Face;
@@ -1408,6 +1409,7 @@ protected
   Boolean has_stream, has_expandable, has_cardinality;
   ConnectionGraph.DaeEdges broken, connected;
 algorithm
+  setGlobalRoot(Global.isInStream, NONE());
   if not topScope then
     return;
   end if;
@@ -2321,7 +2323,7 @@ algorithm
   end if;
 
   positiveMaxCall :=
-    DAE.CALL(Absyn.IDENT("max"), {flowExp, flow_threshold},
+    DAE.CALL(Absyn.IDENT("$OMC$PositiveMax"), {flowExp, flow_threshold},
       DAE.CALL_ATTR(
         ty,
         false,
@@ -2330,6 +2332,8 @@ algorithm
         false,
         DAE.NO_INLINE(),
         DAE.NO_TAIL()));
+
+  setGlobalRoot(Global.isInStream, SOME(true));
 end makePositiveMaxCall;
 
 protected function evaluateConnectionOperators
diff --git a/Compiler/Global/Global.mo b/Compiler/Global/Global.mo
index b72dedf91a9..f19641bce81 100644
--- a/Compiler/Global/Global.mo
+++ b/Compiler/Global/Global.mo
@@ -64,6 +64,7 @@ constant Integer currentInstVar = 22;
 constant Integer operatorOverloadingCache = 23;
 constant Integer optionSimCode = 24;
 constant Integer interactiveCache = 25;
+constant Integer isInStream = 26;
 
 // indexes in System.tick
 // ----------------------