diff --git a/README.md b/README.md
index 683bea0a9..47fa9a247 100644
--- a/README.md
+++ b/README.md
@@ -42,7 +42,7 @@ The source code is published under GPLv3 with OpenSSL exception, the license is
 ## Build instructions
 
 * [Visual Studio 2017][msvc]
-* [Xcode 8][xcode]
+* [Xcode 9][xcode]
 * [GYP/CMake on GNU/Linux][cmake]
 
 [//]: # (LINKS)
diff --git a/Telegram/SourceFiles/core/basic_types.h b/Telegram/SourceFiles/core/basic_types.h
index a6b142a99..b9a07b580 100644
--- a/Telegram/SourceFiles/core/basic_types.h
+++ b/Telegram/SourceFiles/core/basic_types.h
@@ -29,10 +29,7 @@ Copyright (c) 2014-2017 John Preston, https://desktop.telegram.org
 
 using gsl::not_null;
 
-// Custom libc++ build used for old OS X versions already has this.
-#ifndef OS_MAC_OLD
-
-#if defined COMPILER_CLANG || defined COMPILER_GCC
+#if defined COMPILER_GCC
 namespace std {
 
 template <typename T>
@@ -44,9 +41,7 @@ template <typename T>
 void as_const(const T&&) = delete;
 
 } // namespace std
-#endif // COMPILER_CLANG || COMPILER_GCC
-
-#endif // OS_MAC_OLD
+#endif // COMPILER_GCC
 
 #include "base/ordered_set.h"
 
diff --git a/Telegram/SourceFiles/data/data_flags.h b/Telegram/SourceFiles/data/data_flags.h
index 5c78a217b..34f12fcf7 100644
--- a/Telegram/SourceFiles/data/data_flags.h
+++ b/Telegram/SourceFiles/data/data_flags.h
@@ -24,9 +24,12 @@ Copyright (c) 2014-2017 John Preston, https://desktop.telegram.org
 
 namespace Data {
 
+template <typename FlagsType>
+using FlagsUnderlying = typename FlagsType::Type;
+
 template <
 	typename FlagsType,
-	typename FlagsType::Type kEssential = -1>
+	FlagsUnderlying<FlagsType> kEssential = FlagsUnderlying<FlagsType>(-1)>
 class Flags {
 public:
 	using Type = FlagsType;
diff --git a/Telegram/SourceFiles/mtproto/core_types.h b/Telegram/SourceFiles/mtproto/core_types.h
index 19015c31d..f4997e69c 100644
--- a/Telegram/SourceFiles/mtproto/core_types.h
+++ b/Telegram/SourceFiles/mtproto/core_types.h
@@ -370,7 +370,7 @@ public:
 	void read(const mtpPrime *&from, const mtpPrime *end, mtpTypeId cons = mtpc_flags) {
 		if (from + 1 > end) throw mtpErrorInsufficient();
 		if (cons != mtpc_flags) throw mtpErrorUnexpected(cons, "MTPflags");
-		v = Flags::from_raw(static_cast<Flags::Type>(*(from++)));
+		v = Flags::from_raw(static_cast<typename Flags::Type>(*(from++)));
 	}
 	void write(mtpBuffer &to) const {
 		to.push_back(static_cast<mtpPrime>(v.value()));
diff --git a/Telegram/SourceFiles/rpl/combine.h b/Telegram/SourceFiles/rpl/combine.h
index e9d209e50..4a0284354 100644
--- a/Telegram/SourceFiles/rpl/combine.h
+++ b/Telegram/SourceFiles/rpl/combine.h
@@ -21,6 +21,7 @@ Copyright (c) 2014-2017 John Preston, https://desktop.telegram.org
 #pragma once
 
 #include "base/optional.h"
+#include <rpl/map.h>
 #include <rpl/producer.h>
 #include <rpl/details/type_list.h>
 #include <rpl/details/callable.h>
diff --git a/Telegram/SourceFiles/rpl/combine_previous.h b/Telegram/SourceFiles/rpl/combine_previous.h
index 6c4a6c826..000a14b54 100644
--- a/Telegram/SourceFiles/rpl/combine_previous.h
+++ b/Telegram/SourceFiles/rpl/combine_previous.h
@@ -42,7 +42,7 @@ public:
 			return std::move(initial).start(
 				[consumer, previous](auto &&value) {
 					if (auto exists = *previous) {
-						&existing = *exists;
+						auto &existing = *exists;
 						auto next = std::make_tuple(
 							std::move(existing),
 							value);
diff --git a/Telegram/SourceFiles/rpl/details/callable.h b/Telegram/SourceFiles/rpl/details/callable.h
index 146f1a479..6f6018adb 100644
--- a/Telegram/SourceFiles/rpl/details/callable.h
+++ b/Telegram/SourceFiles/rpl/details/callable.h
@@ -23,20 +23,12 @@ Copyright (c) 2014-2017 John Preston, https://desktop.telegram.org
 #include "base/build_config.h"
 #include <tuple>
 
-
-// Custom libc++ build used for old OS X versions already has this.
-#ifndef OS_MAC_OLD
-
-#if defined COMPILER_CLANG || defined COMPILER_GCC
-namespace std {
-
 #ifdef COMPILER_GCC
+namespace std {
 
 template <bool Value>
 using bool_constant = integral_constant<bool, Value>;
 
-#endif // COMPILER_GCC
-
 template <typename ...Args>
 constexpr auto tuple_size_v = std::tuple_size<Args...>::value;
 
@@ -70,9 +62,7 @@ constexpr decltype(auto) apply(Method &&method, Tuple&& tuple) {
 }
 
 } // namespace std
-#endif // COMPILER_CLANG || COMPILER_GCC
-
-#endif // OS_MAC_OLD
+#endif // COMPILER_GCC
 
 namespace rpl {
 namespace details {
diff --git a/Telegram/SourceFiles/rpl/range.h b/Telegram/SourceFiles/rpl/range.h
index 58fc9dc70..089a6aef8 100644
--- a/Telegram/SourceFiles/rpl/range.h
+++ b/Telegram/SourceFiles/rpl/range.h
@@ -56,6 +56,18 @@ inline producer<Value, Error> vector(std::vector<Value> &&values) {
 	};
 }
 
+template <typename Error = no_error>
+inline producer<bool, Error> vector(std::vector<bool> &&values) {
+	return [values = std::move(values)](
+			const consumer<bool, Error> &consumer) mutable {
+		for (auto value : values) {
+			consumer.put_next_copy(value);
+		}
+		consumer.put_done();
+		return lifetime();
+	};
+}
+
 template <typename Value, typename Error = no_error, typename Range>
 inline producer<Value, Error> range(Range &&range) {
 	return vector(std::vector<Value>(
diff --git a/Telegram/SourceFiles/ui/rp_widget.h b/Telegram/SourceFiles/ui/rp_widget.h
index fce9f5f38..53697428b 100644
--- a/Telegram/SourceFiles/ui/rp_widget.h
+++ b/Telegram/SourceFiles/ui/rp_widget.h
@@ -41,7 +41,7 @@ public:
 
 	rpl::producer<QRect> geometryValue() const {
 		auto &stream = eventStreams().geometry;
-		return stream.events_starting_with_copy(geometry());
+		return stream.events_starting_with_copy(this->geometry());
 	}
 	rpl::producer<QSize> sizeValue() const {
 		return geometryValue()
@@ -88,7 +88,7 @@ public:
 	void showOn(rpl::producer<bool> &&shown) {
 		std::move(shown)
 			| rpl::start([this](bool visible) {
-				setVisible(visible);
+				this->setVisible(visible);
 			}, lifetime());
 	}
 
@@ -103,7 +103,7 @@ protected:
 		case QEvent::Resize:
 			if (auto streams = _eventStreams.get()) {
 				auto that = weak(this);
-				streams->geometry.fire_copy(geometry());
+				streams->geometry.fire_copy(this->geometry());
 				if (!that) {
 					return true;
 				}
diff --git a/Telegram/gyp/refresh.sh b/Telegram/gyp/refresh.sh
index d9e90a16b..f16d9f414 100755
--- a/Telegram/gyp/refresh.sh
+++ b/Telegram/gyp/refresh.sh
@@ -28,7 +28,7 @@ else
   #gyp --depth=. --generator-output=../.. -Goutput_dir=out Telegram.gyp --format=xcode-ninja
   #gyp --depth=. --generator-output=../.. -Goutput_dir=out Telegram.gyp --format=xcode
   # use patched gyp with Xcode project generator
-  ../../../Libraries/gyp/gyp --depth=. --generator-output=.. -Goutput_dir=../out -Gxcode_upgrade_check_project_version=830 -Dofficial_build_target=$BuildTarget Telegram.gyp --format=xcode
+  ../../../Libraries/gyp/gyp --depth=. --generator-output=.. -Goutput_dir=../out -Gxcode_upgrade_check_project_version=900 -Dofficial_build_target=$BuildTarget Telegram.gyp --format=xcode
 fi
 
 cd ../..
diff --git a/docs/building-xcode-old.md b/docs/building-xcode-old.md
index af6367ad4..7ba63ad27 100644
--- a/docs/building-xcode-old.md
+++ b/docs/building-xcode-old.md
@@ -1,4 +1,4 @@
-## Build instructions for Xcode 7.2.1
+## Build instructions for Xcode 9.0
 
 **NB** These are outdated, please refer to [Building using Xcode][xcode] instructions.
 
diff --git a/docs/building-xcode.md b/docs/building-xcode.md
index 9fa0d7420..f8fc7b6d2 100644
--- a/docs/building-xcode.md
+++ b/docs/building-xcode.md
@@ -1,4 +1,4 @@
-## Build instructions for Xcode 8.0
+## Build instructions for Xcode 9.0
 
 ### Prepare folder