diff --git a/src/Analyser/TypeSpecifier.php b/src/Analyser/TypeSpecifier.php
index 4deacb787e..d73a9b7984 100644
--- a/src/Analyser/TypeSpecifier.php
+++ b/src/Analyser/TypeSpecifier.php
@@ -183,148 +183,10 @@ public function specifyTypesInCondition(
 				$exprNode = $expressions[0];
 				/** @var ConstantScalarType $constantType */
 				$constantType = $expressions[1];
-				if (!$context->null() && $constantType->getValue() === false) {
-					$types = $this->create($exprNode, $constantType, $context, false, $scope, $rootExpr);
-					return $types->unionWith($this->specifyTypesInCondition(
-						$scope,
-						$exprNode,
-						$context->true() ? TypeSpecifierContext::createFalse() : TypeSpecifierContext::createFalse()->negate(),
-						$rootExpr,
-					));
-				}
 
-				if (!$context->null() && $constantType->getValue() === true) {
-					$types = $this->create($exprNode, $constantType, $context, false, $scope, $rootExpr);
-					return $types->unionWith($this->specifyTypesInCondition(
-						$scope,
-						$exprNode,
-						$context->true() ? TypeSpecifierContext::createTrue() : TypeSpecifierContext::createTrue()->negate(),
-						$rootExpr,
-					));
-				}
-
-				if ($constantType->getValue() === null) {
-					return $this->create($exprNode, $constantType, $context, false, $scope, $rootExpr);
-				}
-
-				if (
-					!$context->null()
-					&& $exprNode instanceof FuncCall
-					&& count($exprNode->getArgs()) === 1
-					&& $exprNode->name instanceof Name
-					&& in_array(strtolower((string) $exprNode->name), ['count', 'sizeof'], true)
-					&& $constantType instanceof ConstantIntegerType
-				) {
-					if ($context->truthy() || $constantType->getValue() === 0) {
-						$newContext = $context;
-						if ($constantType->getValue() === 0) {
-							$newContext = $newContext->negate();
-						}
-						$argType = $scope->getType($exprNode->getArgs()[0]->value);
-						if ($argType->isArray()->yes()) {
-							$funcTypes = $this->create($exprNode, $constantType, $context, false, $scope, $rootExpr);
-							$valueTypes = $this->create($exprNode->getArgs()[0]->value, new NonEmptyArrayType(), $newContext, false, $scope, $rootExpr);
-							return $funcTypes->unionWith($valueTypes);
-						}
-					}
-				}
-
-				if (
-					!$context->null()
-					&& $exprNode instanceof FuncCall
-					&& count($exprNode->getArgs()) === 1
-					&& $exprNode->name instanceof Name
-					&& strtolower((string) $exprNode->name) === 'strlen'
-					&& $constantType instanceof ConstantIntegerType
-				) {
-					if ($context->truthy() || $constantType->getValue() === 0) {
-						$newContext = $context;
-						if ($constantType->getValue() === 0) {
-							$newContext = $newContext->negate();
-						}
-						$argType = $scope->getType($exprNode->getArgs()[0]->value);
-						if ($argType->isString()->yes()) {
-							$funcTypes = $this->create($exprNode, $constantType, $context, false, $scope, $rootExpr);
-
-							$accessory = new AccessoryNonEmptyStringType();
-							if ($constantType->getValue() >= 2) {
-								$accessory = new AccessoryNonFalsyStringType();
-							}
-							$valueTypes = $this->create($exprNode->getArgs()[0]->value, $accessory, $newContext, false, $scope, $rootExpr);
-
-							return $funcTypes->unionWith($valueTypes);
-						}
-					}
-				}
-
-				if (
-					$context->truthy()
-					&& $exprNode instanceof FuncCall
-					&& $exprNode->name instanceof Name
-					&& in_array(strtolower($exprNode->name->toString()), ['substr', 'strstr', 'stristr', 'strchr', 'strrchr', 'strtolower', 'strtoupper', 'mb_strtolower', 'mb_strtoupper', 'ucfirst', 'lcfirst', 'ucwords'], true)
-					&& isset($exprNode->getArgs()[0])
-					&& $constantType instanceof ConstantStringType
-					&& $constantType->getValue() !== ''
-				) {
-					$argType = $scope->getType($exprNode->getArgs()[0]->value);
-
-					if ($argType->isString()->yes()) {
-						if ($constantType->getValue() !== '0') {
-							return $this->create(
-								$exprNode->getArgs()[0]->value,
-								TypeCombinator::intersect($argType, new AccessoryNonFalsyStringType()),
-								$context,
-								false,
-								$scope,
-							);
-						}
-
-						return $this->create(
-							$exprNode->getArgs()[0]->value,
-							TypeCombinator::intersect($argType, new AccessoryNonEmptyStringType()),
-							$context,
-							false,
-							$scope,
-						);
-					}
-				}
-
-				if (
-					$exprNode instanceof FuncCall
-					&& $exprNode->name instanceof Name
-					&& strtolower($exprNode->name->toString()) === 'gettype'
-					&& isset($exprNode->getArgs()[0])
-					&& $constantType instanceof ConstantStringType
-				) {
-					$type = null;
-					if ($constantType->getValue() === 'string') {
-						$type = new StringType();
-					}
-					if ($constantType->getValue() === 'array') {
-						$type = new ArrayType(new MixedType(), new MixedType());
-					}
-					if ($constantType->getValue() === 'boolean') {
-						$type = new BooleanType();
-					}
-					if ($constantType->getValue() === 'resource' || $constantType->getValue() === 'resource (closed)') {
-						$type = new ResourceType();
-					}
-					if ($constantType->getValue() === 'integer') {
-						$type = new IntegerType();
-					}
-					if ($constantType->getValue() === 'double') {
-						$type = new FloatType();
-					}
-					if ($constantType->getValue() === 'NULL') {
-						$type = new NullType();
-					}
-					if ($constantType->getValue() === 'object') {
-						$type = new ObjectWithoutClassType();
-					}
-
-					if ($type !== null) {
-						return $this->create($exprNode->getArgs()[0]->value, $type, $context, false, $scope, $rootExpr);
-					}
+				$specifiedType = $this->specifyTypesForConstantBinaryExpression($exprNode, $constantType, $context, $scope, $rootExpr);
+				if ($specifiedType !== null) {
+					return $specifiedType;
 				}
 			}
 
@@ -1034,6 +896,215 @@ public function specifyTypesInCondition(
 		return new SpecifiedTypes([], [], false, [], $rootExpr);
 	}
 
+	private function specifyTypesForConstantBinaryExpression(
+		Expr $exprNode,
+		ConstantScalarType $constantType,
+		TypeSpecifierContext $context,
+		Scope $scope,
+		?Expr $rootExpr,
+	): ?SpecifiedTypes
+	{
+		if (!$context->null() && $constantType->getValue() === false) {
+			$types = $this->create($exprNode, $constantType, $context, false, $scope, $rootExpr);
+			return $types->unionWith($this->specifyTypesInCondition(
+				$scope,
+				$exprNode,
+				$context->true() ? TypeSpecifierContext::createFalse() : TypeSpecifierContext::createFalse()->negate(),
+				$rootExpr,
+			));
+		}
+
+		if (!$context->null() && $constantType->getValue() === true) {
+			$types = $this->create($exprNode, $constantType, $context, false, $scope, $rootExpr);
+			return $types->unionWith($this->specifyTypesInCondition(
+				$scope,
+				$exprNode,
+				$context->true() ? TypeSpecifierContext::createTrue() : TypeSpecifierContext::createTrue()->negate(),
+				$rootExpr,
+			));
+		}
+
+		if ($constantType->getValue() === null) {
+			return $this->create($exprNode, $constantType, $context, false, $scope, $rootExpr);
+		}
+
+		if (
+			!$context->null()
+			&& $exprNode instanceof FuncCall
+			&& count($exprNode->getArgs()) === 1
+			&& $exprNode->name instanceof Name
+			&& in_array(strtolower((string) $exprNode->name), ['count', 'sizeof'], true)
+			&& $constantType instanceof ConstantIntegerType
+		) {
+			if ($context->truthy() || $constantType->getValue() === 0) {
+				$newContext = $context;
+				if ($constantType->getValue() === 0) {
+					$newContext = $newContext->negate();
+				}
+				$argType = $scope->getType($exprNode->getArgs()[0]->value);
+				if ($argType->isArray()->yes()) {
+					$funcTypes = $this->create($exprNode, $constantType, $context, false, $scope, $rootExpr);
+					$valueTypes = $this->create($exprNode->getArgs()[0]->value, new NonEmptyArrayType(), $newContext, false, $scope, $rootExpr);
+					return $funcTypes->unionWith($valueTypes);
+				}
+			}
+		}
+
+		if (
+			!$context->null()
+			&& $exprNode instanceof FuncCall
+			&& count($exprNode->getArgs()) === 1
+			&& $exprNode->name instanceof Name
+			&& strtolower((string) $exprNode->name) === 'strlen'
+			&& $constantType instanceof ConstantIntegerType
+		) {
+			if ($context->truthy() || $constantType->getValue() === 0) {
+				$newContext = $context;
+				if ($constantType->getValue() === 0) {
+					$newContext = $newContext->negate();
+				}
+				$argType = $scope->getType($exprNode->getArgs()[0]->value);
+				if ($argType->isString()->yes()) {
+					$funcTypes = $this->create($exprNode, $constantType, $context, false, $scope, $rootExpr);
+
+					$accessory = new AccessoryNonEmptyStringType();
+					if ($constantType->getValue() >= 2) {
+						$accessory = new AccessoryNonFalsyStringType();
+					}
+					$valueTypes = $this->create($exprNode->getArgs()[0]->value, $accessory, $newContext, false, $scope, $rootExpr);
+
+					return $funcTypes->unionWith($valueTypes);
+				}
+			}
+
+		}
+
+		if ($constantType instanceof ConstantStringType) {
+			return $this->specifyTypesForConstantStringBinaryExpression($exprNode, $constantType, $context, $scope, $rootExpr);
+		}
+
+		return null;
+	}
+
+	private function specifyTypesForConstantStringBinaryExpression(
+		Expr $exprNode,
+		ConstantStringType $constantType,
+		TypeSpecifierContext $context,
+		Scope $scope,
+		?Expr $rootExpr,
+	): ?SpecifiedTypes
+	{
+		if (
+			$context->truthy()
+			&& $exprNode instanceof FuncCall
+			&& $exprNode->name instanceof Name
+			&& in_array(strtolower($exprNode->name->toString()), ['substr', 'strstr', 'stristr', 'strchr', 'strrchr', 'strtolower', 'strtoupper', 'mb_strtolower', 'mb_strtoupper', 'ucfirst', 'lcfirst', 'ucwords'], true)
+			&& isset($exprNode->getArgs()[0])
+			&& $constantType->getValue() !== ''
+		) {
+			$argType = $scope->getType($exprNode->getArgs()[0]->value);
+
+			if ($argType->isString()->yes()) {
+				if ($constantType->getValue() !== '0') {
+					return $this->create(
+						$exprNode->getArgs()[0]->value,
+						TypeCombinator::intersect($argType, new AccessoryNonFalsyStringType()),
+						$context,
+						false,
+						$scope,
+					);
+				}
+
+				return $this->create(
+					$exprNode->getArgs()[0]->value,
+					TypeCombinator::intersect($argType, new AccessoryNonEmptyStringType()),
+					$context,
+					false,
+					$scope,
+				);
+			}
+		}
+
+		if (
+			$exprNode instanceof FuncCall
+			&& $exprNode->name instanceof Name
+			&& strtolower($exprNode->name->toString()) === 'gettype'
+			&& isset($exprNode->getArgs()[0])
+		) {
+			$type = null;
+			if ($constantType->getValue() === 'string') {
+				$type = new StringType();
+			}
+			if ($constantType->getValue() === 'array') {
+				$type = new ArrayType(new MixedType(), new MixedType());
+			}
+			if ($constantType->getValue() === 'boolean') {
+				$type = new BooleanType();
+			}
+			if ($constantType->getValue() === 'resource' || $constantType->getValue() === 'resource (closed)') {
+				$type = new ResourceType();
+			}
+			if ($constantType->getValue() === 'integer') {
+				$type = new IntegerType();
+			}
+			if ($constantType->getValue() === 'double') {
+				$type = new FloatType();
+			}
+			if ($constantType->getValue() === 'NULL') {
+				$type = new NullType();
+			}
+			if ($constantType->getValue() === 'object') {
+				$type = new ObjectWithoutClassType();
+			}
+
+			if ($type !== null) {
+				return $this->create($exprNode->getArgs()[0]->value, $type, $context, false, $scope, $rootExpr);
+			}
+		}
+
+		if (
+			$context->true()
+			&& $exprNode instanceof FuncCall
+			&& $exprNode->name instanceof Name
+			&& strtolower((string) $exprNode->name) === 'get_parent_class'
+			&& isset($exprNode->getArgs()[0])
+		) {
+			$argType = $scope->getType($exprNode->getArgs()[0]->value);
+			$objectType = new ObjectType($constantType->getValue());
+			$classStringType = new GenericClassStringType($objectType);
+
+			if ($argType->isString()->yes()) {
+				return $this->create(
+					$exprNode->getArgs()[0]->value,
+					$classStringType,
+					$context,
+					false,
+					$scope,
+				);
+			}
+
+			if ((new ObjectWithoutClassType())->isSuperTypeOf($argType)->yes()) {
+				return $this->create(
+					$exprNode->getArgs()[0]->value,
+					$objectType,
+					$context,
+					false,
+					$scope,
+				);
+			}
+
+			return $this->create(
+				$exprNode->getArgs()[0]->value,
+				TypeCombinator::union($objectType, $classStringType),
+				$context,
+				false,
+				$scope,
+			);
+		}
+
+		return null;
+	}
+
 	private function handleDefaultTruthyOrFalseyContext(TypeSpecifierContext $context, ?Expr $rootExpr, Expr $expr, Scope $scope): SpecifiedTypes
 	{
 		if ($context->null()) {
diff --git a/tests/PHPStan/Analyser/NodeScopeResolverTest.php b/tests/PHPStan/Analyser/NodeScopeResolverTest.php
index b7f0425f68..ce44abdc56 100644
--- a/tests/PHPStan/Analyser/NodeScopeResolverTest.php
+++ b/tests/PHPStan/Analyser/NodeScopeResolverTest.php
@@ -1050,6 +1050,7 @@ public function dataFileAsserts(): iterable
 
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/array-offset-unset.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-8008.php');
+		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-5552.php');
 	}
 
 	/**
diff --git a/tests/PHPStan/Analyser/data/bug-5552.php b/tests/PHPStan/Analyser/data/bug-5552.php
new file mode 100644
index 0000000000..4b05d1b053
--- /dev/null
+++ b/tests/PHPStan/Analyser/data/bug-5552.php
@@ -0,0 +1,55 @@
+<?php declare(strict_types = 1);
+
+namespace Bug5552;
+
+use function PHPStan\Testing\assertType;
+
+class HelloWorld
+{
+	public function happyPath($mixed, object $o, string $s): void
+	{
+		if (get_parent_class($mixed) === A::class) {
+			assertType('Bug5552\A|class-string<Bug5552\A>', $mixed);
+		} else {
+			assertType('mixed', $mixed);
+		}
+		assertType('mixed', $mixed);
+
+		if (A::class === get_parent_class($mixed)) {
+			assertType('Bug5552\A|class-string<Bug5552\A>', $mixed);
+		} else {
+			assertType('mixed', $mixed);
+		}
+		assertType('mixed', $mixed);
+
+		if (get_parent_class($mixed) === 'Bug5552\A') {
+			assertType('Bug5552\A|class-string<Bug5552\A>', $mixed);
+		} else {
+			assertType('mixed', $mixed);
+		}
+		assertType('mixed', $mixed);
+
+		if ('Bug5552\A' === get_parent_class($mixed)) {
+			assertType('Bug5552\A|class-string<Bug5552\A>', $mixed);
+		} else {
+			assertType('mixed', $mixed);
+		}
+		assertType('mixed', $mixed);
+
+		if (get_parent_class($o) === A::class) {
+			assertType('Bug5552\A', $o);
+		}
+		if (A::class === get_parent_class($o)) {
+			assertType('Bug5552\A', $o);
+		}
+
+		if (get_parent_class($s) === A::class) {
+			assertType('class-string<Bug5552\A>', $s);
+		}
+		if (A::class === get_parent_class($s)) {
+			assertType('class-string<Bug5552\A>', $s);
+		}
+	}
+}
+
+class A {}