diff --git a/api4/post.go b/api4/post.go
index 5a55771e8d..3ee2fa8c13 100644
--- a/api4/post.go
+++ b/api4/post.go
@@ -529,11 +529,9 @@ func getPostThread(c *Context, w http.ResponseWriter, r *http.Request) {
 	}
 
 	fromPost := r.URL.Query().Get("fromPost")
-	// Either both have to be set, or none have to be set.
-	// Setting one and not setting the other is an error.
-	if (fromPost == "" && fromCreateAt != 0) || (fromPost != "" && fromCreateAt == 0) {
-		c.SetInvalidParam("fromPost/fromCreateAt")
-		return
+	// Either only fromCreateAt must be set, or both fromPost and fromCreateAt must be set
+	if fromPost != "" && fromCreateAt == 0 {
+		c.SetInvalidParam("if fromPost is set, then fromCreatAt must also be set")
 	}
 
 	direction := ""
diff --git a/store/sqlstore/post_store.go b/store/sqlstore/post_store.go
index 2368dded54..a9761981da 100644
--- a/store/sqlstore/post_store.go
+++ b/store/sqlstore/post_store.go
@@ -604,23 +604,34 @@ func (s *SqlPostStore) getPostWithCollapsedThreads(id, userID string, opts model
 		query = query.OrderBy("CreateAt " + sort + ", Id " + sort)
 	}
 
-	if opts.FromPost != "" && opts.FromCreateAt != 0 {
+	if opts.FromCreateAt != 0 {
 		if opts.Direction == "down" {
-			query = query.Where(sq.Or{
-				sq.Gt{"Posts.CreateAt": opts.FromCreateAt},
-				sq.And{
-					sq.Eq{"Posts.CreateAt": opts.FromCreateAt},
-					sq.Gt{"Posts.Id": opts.FromPost},
-				},
-			})
+			direction := sq.Gt{"Posts.CreateAt": opts.FromCreateAt}
+			if opts.FromPost != "" {
+				query = query.Where(sq.Or{
+					direction,
+					sq.And{
+						sq.Eq{"Posts.CreateAt": opts.FromCreateAt},
+						sq.Gt{"Posts.Id": opts.FromPost},
+					},
+				})
+			} else {
+				query = query.Where(direction)
+			}
 		} else {
-			query = query.Where(sq.Or{
-				sq.Lt{"Posts.CreateAt": opts.FromCreateAt},
-				sq.And{
-					sq.Eq{"Posts.CreateAt": opts.FromCreateAt},
-					sq.Lt{"Posts.Id": opts.FromPost},
-				},
-			})
+			direction := sq.Lt{"Posts.CreateAt": opts.FromCreateAt}
+			if opts.FromPost != "" {
+				query = query.Where(sq.Or{
+					direction,
+					sq.And{
+						sq.Eq{"Posts.CreateAt": opts.FromCreateAt},
+						sq.Lt{"Posts.Id": opts.FromPost},
+					},
+				})
+
+			} else {
+				query = query.Where(direction)
+			}
 		}
 	}
 
@@ -715,23 +726,34 @@ func (s *SqlPostStore) Get(ctx context.Context, id string, opts model.GetPostsOp
 			query = query.OrderBy("CreateAt " + sort + ", Id " + sort)
 		}
 
-		if opts.FromPost != "" && opts.FromCreateAt != 0 {
+		if opts.FromCreateAt != 0 {
 			if opts.Direction == "down" {
-				query = query.Where(sq.Or{
-					sq.Gt{"p.CreateAt": opts.FromCreateAt},
-					sq.And{
-						sq.Eq{"p.CreateAt": opts.FromCreateAt},
-						sq.Gt{"p.Id": opts.FromPost},
-					},
-				})
+				direction := sq.Gt{"p.CreateAt": opts.FromCreateAt}
+				if opts.FromPost != "" {
+					query = query.Where(sq.Or{
+						direction,
+						sq.And{
+							sq.Eq{"p.CreateAt": opts.FromCreateAt},
+							sq.Gt{"p.Id": opts.FromPost},
+						},
+					})
+				} else {
+					query = query.Where(direction)
+				}
 			} else {
-				query = query.Where(sq.Or{
-					sq.Lt{"p.CreateAt": opts.FromCreateAt},
-					sq.And{
-						sq.Eq{"p.CreateAt": opts.FromCreateAt},
-						sq.Lt{"p.Id": opts.FromPost},
-					},
-				})
+				direction := sq.Lt{"p.CreateAt": opts.FromCreateAt}
+				if opts.FromPost != "" {
+					query = query.Where(sq.Or{
+						direction,
+						sq.And{
+							sq.Eq{"p.CreateAt": opts.FromCreateAt},
+							sq.Lt{"p.Id": opts.FromPost},
+						},
+					})
+
+				} else {
+					query = query.Where(direction)
+				}
 			}
 		}
 
diff --git a/store/storetest/post_store.go b/store/storetest/post_store.go
index 1d98dc9a31..5f095f576a 100644
--- a/store/storetest/post_store.go
+++ b/store/storetest/post_store.go
@@ -567,7 +567,7 @@ func testPostStoreGetForThread(t *testing.T, ss store.Store) {
 		require.NoError(t, err)
 		_, err = ss.Post().Save(&model.Post{ChannelId: o1.ChannelId, UserId: model.NewId(), Message: NewTestId(), RootId: o1.Id})
 		require.NoError(t, err)
-		_, err = ss.Post().Save(&model.Post{ChannelId: o1.ChannelId, UserId: model.NewId(), Message: NewTestId(), RootId: o1.Id})
+		m1, err := ss.Post().Save(&model.Post{ChannelId: o1.ChannelId, UserId: model.NewId(), Message: NewTestId(), RootId: o1.Id})
 		require.NoError(t, err)
 		_, err = ss.Post().Save(&model.Post{ChannelId: o1.ChannelId, UserId: model.NewId(), Message: NewTestId(), RootId: o1.Id})
 		require.NoError(t, err)
@@ -615,6 +615,20 @@ func testPostStoreGetForThread(t *testing.T, ss store.Store) {
 		assert.LessOrEqual(t, r1.Posts[r1.Order[1]].CreateAt, firstPostCreateAt)
 		assert.False(t, r1.HasNext)
 
+		// Only with CreateAt
+		opts = model.GetPostsOptions{
+			CollapsedThreads: false,
+			PerPage:          1,
+			Direction:        "up",
+			FromCreateAt:     m1.CreateAt,
+			SkipFetchThreads: false,
+		}
+		r1, err = ss.Post().Get(context.Background(), o1.Id, opts, o1.UserId)
+		require.NoError(t, err)
+		assert.Len(t, r1.Order, 2) // including the root post
+		assert.LessOrEqual(t, r1.Posts[r1.Order[1]].CreateAt, m1.CreateAt)
+		assert.True(t, r1.HasNext)
+
 		// Non-CRT mode
 		opts = model.GetPostsOptions{
 			CollapsedThreads: false,
@@ -659,6 +673,20 @@ func testPostStoreGetForThread(t *testing.T, ss store.Store) {
 		assert.Len(t, r1.Order, 3) // including the root post
 		assert.LessOrEqual(t, r1.Posts[r1.Order[1]].CreateAt, firstPostCreateAt)
 		assert.False(t, r1.HasNext)
+
+		// Only with CreateAt
+		opts = model.GetPostsOptions{
+			CollapsedThreads: false,
+			PerPage:          1,
+			Direction:        "down",
+			FromCreateAt:     m1.CreateAt,
+			SkipFetchThreads: false,
+		}
+		r1, err = ss.Post().Get(context.Background(), o1.Id, opts, o1.UserId)
+		require.NoError(t, err)
+		assert.Len(t, r1.Order, 2) // including the root post
+		assert.GreaterOrEqual(t, r1.Posts[r1.Order[1]].CreateAt, m1.CreateAt)
+		assert.True(t, r1.HasNext)
 	})
 }