diff --git a/src/Collection/Functions/FetchPropertyFunction.php b/src/Collection/Functions/FetchPropertyFunction.php
index 78d53282..1972d0a8 100644
--- a/src/Collection/Functions/FetchPropertyFunction.php
+++ b/src/Collection/Functions/FetchPropertyFunction.php
@@ -207,6 +207,18 @@ private function processTokens(
 		foreach ($tokens as $tokenIndex => $token) {
 			$property = $currentEntityMetadata->getProperty($token);
 			if ($property->relationship !== null) {
+				$relType = $property->relationship->type;
+				$isMainSide = $relType === Relationship::MANY_HAS_ONE
+					|| ($relType === Relationship::ONE_HAS_ONE && $property->relationship->isMain);
+				if (
+					$isMainSide
+					&& $tokenIndex === count($tokens) - 1
+					&& in_array($lastToken, $property->relationship->entityMetadata->getPrimaryKey(), strict: true)
+				) {
+					$lastToken = $token;
+					break;
+				}
+
 				[
 					$currentAlias,
 					$currentConventions,
@@ -241,6 +253,36 @@ private function processTokens(
 			throw new InvalidArgumentException("Property expression '$propertyExpression' does not fetch specific property.");
 		}
 
+		if ($propertyMetadata->relationship !== null) {
+			$relType = $propertyMetadata->relationship->type;
+			if (
+				($relType === Relationship::ONE_HAS_ONE && !$propertyMetadata->relationship->isMain) ||
+				$relType === Relationship::ONE_HAS_MANY ||
+				$relType === Relationship::MANY_HAS_MANY
+			) {
+				$allTokens = [...$tokens, $lastToken];
+				[
+					$currentAlias,
+					$currentConventions,
+					$currentEntityMetadata,
+				] = $this->processRelationship(
+					$allTokens,
+					$joins,
+					$propertyMetadata,
+					$aggregator,
+					$currentConventions,
+					$currentMapper,
+					$currentAlias,
+					$lastToken,
+					count($allTokens) - 1,
+					$makeDistinct,
+				);
+				$primaryKey = $currentEntityMetadata->getPrimaryKey();
+				$lastToken = $primaryKey[0];
+				$propertyMetadata = $currentEntityMetadata->getProperty($lastToken);
+			}
+		}
+
 		$column = $this->toColumnExpr(
 			$currentEntityMetadata,
 			$propertyMetadata,
diff --git a/tests/cases/integration/Collection/collection.where.phpt b/tests/cases/integration/Collection/collection.where.phpt
index c6789d07..103b102d 100644
--- a/tests/cases/integration/Collection/collection.where.phpt
+++ b/tests/cases/integration/Collection/collection.where.phpt
@@ -175,6 +175,40 @@ class CollectionWhereTest extends DataTestCase
 	}
 
 
+	public function testFilterByNonMainSideRelationship(): void
+	{
+		// Non-main side of 1:1 relationship (Ean.book is non-main, FK ean_id is in books table)
+		$ean = new Ean();
+		$ean->code = '1234';
+		$ean->book = $this->orm->books->getByIdChecked(1);
+		$this->orm->eans->persistAndFlush($ean);
+		$this->orm->clear();
+
+		$fetched = $this->orm->eans->findBy(['book' => 1])->fetch();
+		Assert::notNull($fetched);
+		Assert::equal('1234', $fetched->code);
+
+		Assert::null($this->orm->eans->findBy(['book' => 2])->fetch());
+	}
+
+
+	public function testFilterByNonMainSideRelationshipNull(): void
+	{
+		// Non-main side of 1:1 self-referential relationship (Book.previousPart is non-main side)
+		// Book 4 has next_part = 3, so Book 3 has a previousPart (= Book 4)
+		// Books 1, 2, 4 have no previousPart
+
+		$booksWithNoPrevious = $this->orm->books->findBy(['previousPart' => null]);
+		Assert::count(3, $booksWithNoPrevious);
+
+		$booksWithPrevious = $this->orm->books->findBy(['previousPart!=' => null]);
+		Assert::count(1, $booksWithPrevious);
+		$book = $booksWithPrevious->fetch();
+		Assert::notNull($book);
+		Assert::equal(3, $book->id);
+	}
+
+
 	private function moveToDifferentZone(DateTimeImmutable $dateTime): DateTimeImmutable
 	{
 		return $dateTime->setTimezone(new DateTimeZone("UTC"));
diff --git a/tests/sqls/NextrasTests/Orm/Integration/Collection/CollectionAggregationJoinTest_testAnyDependent.sql b/tests/sqls/NextrasTests/Orm/Integration/Collection/CollectionAggregationJoinTest_testAnyDependent.sql
index 942b99a7..6cc87b1d 100644
--- a/tests/sqls/NextrasTests/Orm/Integration/Collection/CollectionAggregationJoinTest_testAnyDependent.sql
+++ b/tests/sqls/NextrasTests/Orm/Integration/Collection/CollectionAggregationJoinTest_testAnyDependent.sql
@@ -5,13 +5,10 @@ FROM
   LEFT JOIN "books" AS "books_any" ON (
     "authors"."id" = "books_any"."author_id"
   )
-  LEFT JOIN "public"."authors" AS "books_translator_any" ON (
-    "books_any"."translator_id" = "books_translator_any"."id"
-  )
 WHERE
   ("books_any"."title" = 'Book 1')
   AND (
-    "books_translator_any"."id" IS NULL
+    "books_any"."translator_id" IS NULL
   )
 GROUP BY
   "authors"."id";
@@ -27,13 +24,10 @@ FROM
       LEFT JOIN "books" AS "books_any" ON (
         "authors"."id" = "books_any"."author_id"
       )
-      LEFT JOIN "public"."authors" AS "books_translator_any" ON (
-        "books_any"."translator_id" = "books_translator_any"."id"
-      )
     WHERE
       ("books_any"."title" = 'Book 1')
       AND (
-        "books_translator_any"."id" IS NULL
+        "books_any"."translator_id" IS NULL
       )
     GROUP BY
       "authors"."id"
@@ -45,7 +39,10 @@ FROM
   "public"."authors" AS "authors"
   LEFT JOIN "books" AS "books_count" ON (
     (
-      "authors"."id" = "books_count"."author_id"
+      (
+        "authors"."id" = "books_count"."author_id"
+      )
+      AND "books_count"."translator_id" IS NOT NULL
     )
     OR (
       (
@@ -54,18 +51,12 @@ FROM
       AND "books_count"."price" < 100
     )
   )
-  LEFT JOIN "public"."authors" AS "books_translator_count" ON (
-    (
-      "books_count"."translator_id" = "books_translator_count"."id"
-    )
-    AND "books_translator_count"."id" IS NOT NULL
-  )
 GROUP BY
   "authors"."id"
 HAVING
   (
-    COUNT("books_translator_count"."id") >= 1
-    AND COUNT("books_translator_count"."id") <= 1
+    COUNT("books_count"."id") >= 1
+    AND COUNT("books_count"."id") <= 1
   )
   OR (
     COUNT("books_count"."id") >= 1
@@ -82,7 +73,10 @@ FROM
       "public"."authors" AS "authors"
       LEFT JOIN "books" AS "books_count" ON (
         (
-          "authors"."id" = "books_count"."author_id"
+          (
+            "authors"."id" = "books_count"."author_id"
+          )
+          AND "books_count"."translator_id" IS NOT NULL
         )
         OR (
           (
@@ -91,18 +85,12 @@ FROM
           AND "books_count"."price" < 100
         )
       )
-      LEFT JOIN "public"."authors" AS "books_translator_count" ON (
-        (
-          "books_count"."translator_id" = "books_translator_count"."id"
-        )
-        AND "books_translator_count"."id" IS NOT NULL
-      )
     GROUP BY
       "authors"."id"
     HAVING
       (
-        COUNT("books_translator_count"."id") >= 1
-        AND COUNT("books_translator_count"."id") <= 1
+        COUNT("books_count"."id") >= 1
+        AND COUNT("books_count"."id") <= 1
       )
       OR (
         COUNT("books_count"."id") >= 1
diff --git a/tests/sqls/NextrasTests/Orm/Integration/Collection/CollectionTest_testCountStoredAndFutureFiltering.sql b/tests/sqls/NextrasTests/Orm/Integration/Collection/CollectionTest_testCountStoredAndFutureFiltering.sql
index 59fa3124..2e909231 100644
--- a/tests/sqls/NextrasTests/Orm/Integration/Collection/CollectionTest_testCountStoredAndFutureFiltering.sql
+++ b/tests/sqls/NextrasTests/Orm/Integration/Collection/CollectionTest_testCountStoredAndFutureFiltering.sql
@@ -1,26 +1,2 @@
-SELECT
-  COUNT(*) AS count
-FROM
-  (
-    SELECT
-      "books"."id"
-    FROM
-      "books" AS "books"
-      LEFT JOIN "public"."authors" AS "author" ON (
-        "books"."author_id" = "author"."id"
-      )
-    WHERE
-      "author"."id" > 0
-  ) temp;
-
-SELECT
-  "books".*
-FROM
-  "books" AS "books"
-  LEFT JOIN "public"."authors" AS "author" ON (
-    "books"."author_id" = "author"."id"
-  )
-WHERE
-  "author"."id" > 0
-ORDER BY
-  "author"."id" ASC;
+SELECT COUNT(*) AS count FROM (SELECT "books"."id" FROM "books" AS "books" WHERE "books"."author_id" > 0) temp;
+SELECT "books".* FROM "books" AS "books" WHERE "books"."author_id" > 0 ORDER BY "books"."author_id" ASC;
diff --git a/tests/sqls/NextrasTests/Orm/Integration/Collection/CollectionTest_testOrdering.sql b/tests/sqls/NextrasTests/Orm/Integration/Collection/CollectionTest_testOrdering.sql
index 44252c50..980a2ec9 100644
--- a/tests/sqls/NextrasTests/Orm/Integration/Collection/CollectionTest_testOrdering.sql
+++ b/tests/sqls/NextrasTests/Orm/Integration/Collection/CollectionTest_testOrdering.sql
@@ -1,21 +1,2 @@
-SELECT
-  "books".*
-FROM
-  "books" AS "books"
-  LEFT JOIN "public"."authors" AS "author" ON (
-    "books"."author_id" = "author"."id"
-  )
-ORDER BY
-  "author"."id" DESC,
-  "books"."title" ASC;
-
-SELECT
-  "books".*
-FROM
-  "books" AS "books"
-  LEFT JOIN "public"."authors" AS "author" ON (
-    "books"."author_id" = "author"."id"
-  )
-ORDER BY
-  "author"."id" DESC,
-  "books"."title" DESC;
+SELECT "books".* FROM "books" AS "books" ORDER BY "books"."author_id" DESC, "books"."title" ASC;
+SELECT "books".* FROM "books" AS "books" ORDER BY "books"."author_id" DESC, "books"."title" DESC;
diff --git a/tests/sqls/NextrasTests/Orm/Integration/Collection/CollectionTest_testOrderingMultiple.sql b/tests/sqls/NextrasTests/Orm/Integration/Collection/CollectionTest_testOrderingMultiple.sql
index 44252c50..980a2ec9 100644
--- a/tests/sqls/NextrasTests/Orm/Integration/Collection/CollectionTest_testOrderingMultiple.sql
+++ b/tests/sqls/NextrasTests/Orm/Integration/Collection/CollectionTest_testOrderingMultiple.sql
@@ -1,21 +1,2 @@
-SELECT
-  "books".*
-FROM
-  "books" AS "books"
-  LEFT JOIN "public"."authors" AS "author" ON (
-    "books"."author_id" = "author"."id"
-  )
-ORDER BY
-  "author"."id" DESC,
-  "books"."title" ASC;
-
-SELECT
-  "books".*
-FROM
-  "books" AS "books"
-  LEFT JOIN "public"."authors" AS "author" ON (
-    "books"."author_id" = "author"."id"
-  )
-ORDER BY
-  "author"."id" DESC,
-  "books"."title" DESC;
+SELECT "books".* FROM "books" AS "books" ORDER BY "books"."author_id" DESC, "books"."title" ASC;
+SELECT "books".* FROM "books" AS "books" ORDER BY "books"."author_id" DESC, "books"."title" DESC;
diff --git a/tests/sqls/NextrasTests/Orm/Integration/Collection/CollectionWhereTest_testFilterByNonMainSideRelationship.sql b/tests/sqls/NextrasTests/Orm/Integration/Collection/CollectionWhereTest_testFilterByNonMainSideRelationship.sql
new file mode 100644
index 00000000..aa945ce6
--- /dev/null
+++ b/tests/sqls/NextrasTests/Orm/Integration/Collection/CollectionWhereTest_testFilterByNonMainSideRelationship.sql
@@ -0,0 +1,21 @@
+SELECT "books".* FROM "books" AS "books" WHERE "books"."id" = 1;
+START TRANSACTION;
+INSERT INTO "eans" ("code", "type") VALUES ('1234', 2);
+SELECT CURRVAL('public.eans_id_seq');
+UPDATE "books" SET "ean_id" = 1 WHERE "id" = 1;
+COMMIT;
+SELECT
+  "eans".*
+FROM
+  "eans" AS "eans"
+  LEFT JOIN "books" AS "book" ON ("eans"."id" = "book"."ean_id")
+WHERE
+  "book"."id" = 1;
+
+SELECT
+  "eans".*
+FROM
+  "eans" AS "eans"
+  LEFT JOIN "books" AS "book" ON ("eans"."id" = "book"."ean_id")
+WHERE
+  "book"."id" = 2;
diff --git a/tests/sqls/NextrasTests/Orm/Integration/Collection/CollectionWhereTest_testFilterByNonMainSideRelationshipNull.sql b/tests/sqls/NextrasTests/Orm/Integration/Collection/CollectionWhereTest_testFilterByNonMainSideRelationshipNull.sql
new file mode 100644
index 00000000..c26d7954
--- /dev/null
+++ b/tests/sqls/NextrasTests/Orm/Integration/Collection/CollectionWhereTest_testFilterByNonMainSideRelationshipNull.sql
@@ -0,0 +1,19 @@
+SELECT
+  "books".*
+FROM
+  "books" AS "books"
+  LEFT JOIN "books" AS "previousPart" ON (
+    "books"."id" = "previousPart"."next_part"
+  )
+WHERE
+  "previousPart"."id" IS NULL;
+
+SELECT
+  "books".*
+FROM
+  "books" AS "books"
+  LEFT JOIN "books" AS "previousPart" ON (
+    "books"."id" = "previousPart"."next_part"
+  )
+WHERE
+  "previousPart"."id" IS NOT NULL;
diff --git a/tests/sqls/NextrasTests/Orm/Integration/Relationships/RelationshipManyHasManyTest_testCountStoredOnManyHasManyRelationshipCondition.sql b/tests/sqls/NextrasTests/Orm/Integration/Relationships/RelationshipManyHasManyTest_testCountStoredOnManyHasManyRelationshipCondition.sql
index 1f7c3de6..a55c611a 100644
--- a/tests/sqls/NextrasTests/Orm/Integration/Relationships/RelationshipManyHasManyTest_testCountStoredOnManyHasManyRelationshipCondition.sql
+++ b/tests/sqls/NextrasTests/Orm/Integration/Relationships/RelationshipManyHasManyTest_testCountStoredOnManyHasManyRelationshipCondition.sql
@@ -4,14 +4,11 @@ SELECT
   "books_x_tags"."tag_id"
 FROM
   "books" AS "books"
-  LEFT JOIN "public"."authors" AS "author" ON (
-    "books"."author_id" = "author"."id"
-  )
   LEFT JOIN "books_x_tags" AS "books_x_tags" ON (
     "books_x_tags"."book_id" = "books"."id"
   )
 WHERE
-  ("author"."id" = 1)
+  ("books"."author_id" = 1)
   AND (
     "books_x_tags"."tag_id" IN (1)
   );
@@ -24,14 +21,11 @@ SELECT
   ) AS "count"
 FROM
   "books" AS "books"
-  LEFT JOIN "public"."authors" AS "author" ON (
-    "books"."author_id" = "author"."id"
-  )
   LEFT JOIN "books_x_tags" AS "books_x_tags" ON (
     "books_x_tags"."book_id" = "books"."id"
   )
 WHERE
-  ("author"."id" = 1)
+  ("books"."author_id" = 1)
   AND (
     "books_x_tags"."tag_id" IN (1)
   )
@@ -53,15 +47,12 @@ FROM
       LEFT JOIN "tag_followers" AS "author_tagFollowers_any" ON (
         "author"."id" = "author_tagFollowers_any"."author_id"
       )
-      LEFT JOIN "public"."authors" AS "author_tagFollowers_author_any" ON (
-        "author_tagFollowers_any"."author_id" = "author_tagFollowers_author_any"."id"
-      )
       LEFT JOIN "books_x_tags" AS "books_x_tags" ON (
         "books_x_tags"."book_id" = "books"."id"
       )
     WHERE
       (
-        "author_tagFollowers_author_any"."id" = 1
+        "author_tagFollowers_any"."author_id" = 1
       )
       AND (
         "books_x_tags"."tag_id" IN (1)
@@ -89,15 +80,12 @@ FROM
   LEFT JOIN "tag_followers" AS "author_tagFollowers_any" ON (
     "author"."id" = "author_tagFollowers_any"."author_id"
   )
-  LEFT JOIN "public"."authors" AS "author_tagFollowers_author_any" ON (
-    "author_tagFollowers_any"."author_id" = "author_tagFollowers_author_any"."id"
-  )
   LEFT JOIN "books_x_tags" AS "books_x_tags" ON (
     "books_x_tags"."book_id" = "books"."id"
   )
 WHERE
   (
-    "author_tagFollowers_author_any"."id" = 1
+    "author_tagFollowers_any"."author_id" = 1
   )
   AND (
     "books_x_tags"."tag_id" IN (1)