diff --git a/Tsi1.Api/Tsi1.BusinessLayer/Services/PostMessageService.cs b/Tsi1.Api/Tsi1.BusinessLayer/Services/PostMessageService.cs
index 626f981915d68af45e78b62141d9d09d8c0fb9ce..7d7431ffdec334c55948163b4d7b99cf956344a9 100644
--- a/Tsi1.Api/Tsi1.BusinessLayer/Services/PostMessageService.cs
+++ b/Tsi1.Api/Tsi1.BusinessLayer/Services/PostMessageService.cs
@@ -72,7 +72,7 @@ namespace Tsi1.BusinessLayer.Services
 
             var postMessageDtos = _mapper.Map<List<PostMessagePreviewDto>>(postMessages);
 
-            var userIds = postMessageDtos.Select(x => x.UserId);
+            var userIds = postMessageDtos.Select(x => x.UserId).ToList();
 
             var users = await _context.Users.Where(x => userIds.Contains(x.Id)).ToListAsync();
 
diff --git a/Tsi1.Api/Tsi1.BusinessLayer/Services/PostService.cs b/Tsi1.Api/Tsi1.BusinessLayer/Services/PostService.cs
index d039f7e5e640ded9d4a06352b8dc061fa7ce7212..5c52e399ce5fc8678b7e11d10af01495a2abeb78 100644
--- a/Tsi1.Api/Tsi1.BusinessLayer/Services/PostService.cs
+++ b/Tsi1.Api/Tsi1.BusinessLayer/Services/PostService.cs
@@ -72,7 +72,7 @@ namespace Tsi1.BusinessLayer.Services
 
             var postDtos = _mapper.Map<List<PostPreviewDto>>(posts);
 
-            var userIds = postDtos.Select(x => x.UserId);
+            var userIds = postDtos.Select(x => x.UserId).ToList();
 
             var users = await _context.Users.Where(x => userIds.Contains(x.Id)).ToListAsync();