diff --git a/src/ce_common.pas b/src/ce_common.pas
index 4c91ba17..f1781798 100644
--- a/src/ce_common.pas
+++ b/src/ce_common.pas
@@ -265,11 +265,6 @@ type
    *)
   function isStringDisabled(const str: string): boolean;
 
-  (**
-   * Deletes the duplicates in a TStrings instance.
-   *)
-  procedure deleteDups(str: TStrings);
-
   (**
    * Indicates wether str is only made of blank characters
    *)
@@ -1176,19 +1171,6 @@ begin
     result := true;
 end;
 
-procedure deleteDups(str: TStrings);
-var
-  i: integer;
-begin
-  {$PUSH}{$HINTS OFF}
-  if str = nil then exit;
-  for i:= str.Count-1 downto 0 do
-    // if less than 0 -> not found -> unsigned -> greater than current index.
-    if cardinal(str.IndexOf(str[i])) <  i then
-      str.Delete(i);
-  {$POP}
-end;
-
 function isBlank(const str: string): boolean;
 var
   c: char;
diff --git a/src/ce_dubproject.pas b/src/ce_dubproject.pas
index f18ef0ca..dadeef08 100644
--- a/src/ce_dubproject.pas
+++ b/src/ce_dubproject.pas
@@ -274,6 +274,10 @@ begin
   fConfigs := TStringList.Create;
   fSrcs := TStringList.Create;
   fImportPaths := TStringList.Create;
+  fSrcs.Duplicates:=TDuplicates.dupIgnore;
+  fImportPaths.Duplicates:=TDuplicates.dupIgnore;
+  fConfigs.Duplicates:=TDuplicates.dupIgnore;
+  fBuildTypes.Duplicates:=TDuplicates.dupIgnore;
   //
   subjProjNew(fProjectSubject, self);
   subjProjChanged(fProjectSubject, self);
@@ -844,7 +848,6 @@ begin
           tryAddRelOrAbsFile(arr.Strings[i]);
       end;
     end;
-    deleteDups(fSrcs);
     // exclusions
     lst.Clear;
     getExclusion(fJSON);
diff --git a/src/ce_main.pas b/src/ce_main.pas
index 3e463681..834bd63d 100644
--- a/src/ce_main.pas
+++ b/src/ce_main.pas
@@ -2608,6 +2608,7 @@ begin
       ldc: dmdProc.Executable :='ldmd2' + exeExt;
       gdc: dmdProc.Executable :='gdmd'  + exeExt;
     end;
+    TStringList(dmdproc.Parameters).Duplicates:=TDuplicates.dupIgnore;
     dmdproc.Parameters.Add(fDoc.fileName);
     if not asObj then
       dmdproc.Parameters.Add('-of' + fname + exeExt)
@@ -2645,8 +2646,6 @@ begin
       LibMan.getLibFiles(nil, dmdproc.Parameters);
       LibMan.getLibSourcePath(nil, dmdproc.Parameters);
     end;
-
-    deleteDups(dmdproc.Parameters);
     dmdproc.Execute;
     while dmdproc.Running do
       application.ProcessMessages;
diff --git a/src/ce_nativeproject.pas b/src/ce_nativeproject.pas
index b989cabb..a533230f 100644
--- a/src/ce_nativeproject.pas
+++ b/src/ce_nativeproject.pas
@@ -37,7 +37,7 @@ type
     fRunnerOldCwd: string;
     fLibAliases: TStringList;
     fConfigs: TCollection;
-    fSrcs, fSrcsCop: TStringList;
+    fSrcs: TStringList;
     fConfIx: Integer;
     fUpdateCount: NativeInt;
     fProjectSubject: TCEProjectSubject;
@@ -151,9 +151,10 @@ begin
   fProjectSubject := TCEProjectSubject.create;
   //
   fLibAliases := TStringList.Create;
+  fLibAliases.Duplicates:=TDuplicates.dupIgnore;
   fSrcs := TStringList.Create;
+  fSrcs.Duplicates:=TDuplicates.dupIgnore;
   fSrcs.OnChange := @subMemberChanged;
-  fSrcsCop := TStringList.Create;
   fConfigs := TCollection.create(TCompilerConfiguration);
   //
   reset;
@@ -177,7 +178,6 @@ begin
   fOnChange := nil;
   fLibAliases.Free;
   fSrcs.free;
-  fSrcsCop.Free;
   fConfigs.free;
   killProcess(fRunner);
   inherited;