diff --git a/repertory.iss.in b/repertory.iss.in
index b6175feb..bf2ddb61 100644
--- a/repertory.iss.in
+++ b/repertory.iss.in
@@ -32,16 +32,19 @@ WizardStyle=modern
 function CheckAddPath(Param: string): boolean;
 var
   CurPath: string;
+  PathPos: Integer;
 begin
-  if not RegQueryStringValue(HKEY_LOCAL_MACHINE,
+  if RegQueryStringValue(HKEY_LOCAL_MACHINE,
     'SYSTEM\CurrentControlSet\Control\Session Manager\Environment',
-    'Path', CurPath)
+    'PATH', CurPath)
   then begin
-    Result := True;
+    PathPos := Pos(';' + Param + ';', ';' + CurPath + ';');
+    Result := PathPos = 0;
+    MsgBox('Path|' + CurPath + '|Param|' + Param + '|Pos|' + IntToStr(PathPos), mbInformation, MB_OK);
     exit;
   end;
 
-  Result := Pos(';' + Param + ';', ';' + CurPath + ';') = 0;
+  Result := True;
 end;
 
 [Languages]
@@ -66,4 +69,4 @@ Filename: "msiexec.exe"; WorkingDir: "{app}"; Parameters: "/a winfsp-@WINFSP_VER
 [Registry]
 Root: HKLM; Subkey: "SYSTEM\CurrentControlSet\Control\Session Manager\Environment"; \
     ValueType: expandsz; ValueName: "Path"; ValueData: "{olddata};{app};"; \
-    Check: CheckAddPath('{app}')
+    Check: CheckAddPath("{app}")