diff --git a/src/core/Alloc.cpp b/src/core/Alloc.cpp
index 266f2a38..b9ae0922 100644
--- a/src/core/Alloc.cpp
+++ b/src/core/Alloc.cpp
@@ -16,6 +16,7 @@
  */
 
 #include <botan/mem_ops.h>
+#include <cstdlib>
 #if defined(Q_OS_MACOS)
 #include <malloc/malloc.h>
 #elif defined(Q_OS_FREEBSD)
diff --git a/src/gui/osutils/macutils/AppKitImpl.mm b/src/gui/osutils/macutils/AppKitImpl.mm
index 76fe7fe0..a94d9efb 100644
--- a/src/gui/osutils/macutils/AppKitImpl.mm
+++ b/src/gui/osutils/macutils/AppKitImpl.mm
@@ -60,7 +60,7 @@
 - (void) didDeactivateApplicationObserver:(NSNotification*) notification
 {
     NSDictionary* userInfo = notification.userInfo;
-    NSRunningApplication* app = userInfo[NSWorkspaceApplicationKey];
+    NSRunningApplication* app = [userInfo objectForKey:NSWorkspaceApplicationKey];
 
     if (app.processIdentifier != [self ownProcessId]) {
         self.lastActiveApplication = app;
@@ -139,6 +139,7 @@
 //
 - (bool) isStatusBarDark
 {
+#if __clang_major__ >= 9 && MAC_OS_X_VERSION_MIN_REQUIRED >= 101000
     if (@available(macOS 10.17, *)) {
         // This is an ugly hack, but I couldn't find a way to access QTrayIcon's NSStatusItem.
         NSStatusItem* dummy = [[NSStatusBar systemStatusBar] statusItemWithLength:0];
@@ -146,6 +147,7 @@
         [[NSStatusBar systemStatusBar] removeStatusItem:dummy];
         return [appearance containsString:@"dark"];
     }
+#endif
 
     return [self isDarkMode];
 }
@@ -166,9 +168,13 @@
 //
 - (bool) enableAccessibility
 {
+#if MAC_OS_X_VERSION_MIN_REQUIRED >= 1090
     // Request accessibility permissions for Auto-Type type on behalf of the user
     NSDictionary* opts = @{static_cast<id>(kAXTrustedCheckOptionPrompt): @YES};
     return AXIsProcessTrustedWithOptions(static_cast<CFDictionaryRef>(opts));
+#else
+    return YES;
+#endif
 }
 
 //
@@ -176,6 +182,7 @@
 //
 - (bool) enableScreenRecording
 {
+#if __clang_major__ >= 9 && MAC_OS_X_VERSION_MIN_REQUIRED >= 1080
     if (@available(macOS 10.15, *)) {
         // Request screen recording permission on macOS 10.15+
         // This is necessary to get the current window title
@@ -193,6 +200,7 @@
             return NO;
         }
     }
+#endif
     return YES;
 }
 
diff --git a/src/gui/osutils/macutils/MacUtils.cpp b/src/gui/osutils/macutils/MacUtils.cpp
index 6e4b478b..5b475160 100644
--- a/src/gui/osutils/macutils/MacUtils.cpp
+++ b/src/gui/osutils/macutils/MacUtils.cpp
@@ -26,7 +26,10 @@
 #include <QWindow>
 
 #include <ApplicationServices/ApplicationServices.h>
+
+#if MAC_OS_X_VERSION_MIN_REQUIRED >= 1080
 #include <CoreGraphics/CGEventSource.h>
+#endif
 
 #define INVALID_KEYCODE 0xFFFF
 
@@ -138,7 +141,11 @@ void MacUtils::setLaunchAtStartup(bool enable)
 
 bool MacUtils::isCapslockEnabled()
 {
+#if MAC_OS_X_VERSION_MIN_REQUIRED >= 1080
     return (CGEventSourceFlagsState(kCGEventSourceStateHIDSystemState) & kCGEventFlagMaskAlphaShift) != 0;
+#else
+    return false;
+#endif
 }
 
 /**
diff --git a/src/gui/styles/base/BaseStyle.cpp b/src/gui/styles/base/BaseStyle.cpp
index 0068943b..ec3fd9b8 100644
--- a/src/gui/styles/base/BaseStyle.cpp
+++ b/src/gui/styles/base/BaseStyle.cpp
@@ -41,8 +41,10 @@
 
 #ifdef Q_OS_MACOS
 #include <QMainWindow>
+#if QT_VERSION >= QT_VERSION_CHECK(5, 9, 0)
 #include <QOperatingSystemVersion>
 #endif
+#endif
 
 #include "gui/Icons.h"
 
@@ -279,16 +281,22 @@ namespace Phantom
 #ifdef Q_OS_MACOS
             QColor tabBarBase(const QPalette& pal)
             {
+#if QT_VERSION >= QT_VERSION_CHECK(5, 12, 10) && QT_VERSION < QT_VERSION_CHECK(5, 13, 0)                               \
+    || QT_VERSION >= QT_VERSION_CHECK(5, 15, 1)
                 if (QOperatingSystemVersion::current() >= QOperatingSystemVersion::MacOSBigSur) {
                     return hack_isLightPalette(pal) ? QRgb(0xD4D4D4) : QRgb(0x2A2A2A);
                 }
+#endif
                 return hack_isLightPalette(pal) ? QRgb(0xDD1D1D1) : QRgb(0x252525);
             }
             QColor tabBarBaseInactive(const QPalette& pal)
             {
+#if QT_VERSION >= QT_VERSION_CHECK(5, 12, 10) && QT_VERSION < QT_VERSION_CHECK(5, 13, 0)                               \
+    || QT_VERSION >= QT_VERSION_CHECK(5, 15, 1)
                 if (QOperatingSystemVersion::current() >= QOperatingSystemVersion::MacOSBigSur) {
                     return hack_isLightPalette(pal) ? QRgb(0xF5F5F5) : QRgb(0x2D2D2D);
                 }
+#endif
                 return hack_isLightPalette(pal) ? QRgb(0xF4F4F4) : QRgb(0x282828);
             }
 #endif
diff --git a/src/touchid/TouchID.mm b/src/touchid/TouchID.mm
index a2cefecf..7fc9b54a 100644
--- a/src/touchid/TouchID.mm
+++ b/src/touchid/TouchID.mm
@@ -95,6 +95,7 @@ bool TouchID::storeKey(const QString& databasePath, const QByteArray& passwordKe
     // prepare adding secure entry to the macOS KeyChain
     CFErrorRef error = NULL;
     SecAccessControlRef sacObject;
+#if __clang_major__ >= 9 && MAC_OS_X_VERSION_MIN_REQUIRED >= 101500
     if (@available(macOS 10.15, *)) {
         // kSecAccessControlWatch is only available for macOS 10.15 and later
         sacObject = SecAccessControlCreateWithFlags(kCFAllocatorDefault,
@@ -102,11 +103,14 @@ bool TouchID::storeKey(const QString& databasePath, const QByteArray& passwordKe
                                                     kSecAccessControlOr | kSecAccessControlBiometryCurrentSet | kSecAccessControlWatch,
                                                     &error);
     } else {
+#endif
         sacObject = SecAccessControlCreateWithFlags(kCFAllocatorDefault,
                                                     kSecAttrAccessibleWhenUnlockedThisDeviceOnly,
                                                     kSecAccessControlTouchIDCurrentSet, // depr: kSecAccessControlBiometryCurrentSet,
                                                     &error);
+#if __clang_major__ >= 9 && MAC_OS_X_VERSION_MIN_REQUIRED >= 101500
     }
+#endif
 
 
     if (sacObject == NULL || error != NULL) {
@@ -234,11 +238,15 @@ bool TouchID::isAvailable()
         LAContext* context = [[LAContext alloc] init];
 
         LAPolicy policyCode;
+#if __clang_major__ >= 9 && MAC_OS_X_VERSION_MIN_REQUIRED >= 101500
         if (@available(macOS 10.15, *)) {
             policyCode = LAPolicyDeviceOwnerAuthenticationWithBiometricsOrWatch;
         } else {
+#endif
             policyCode = LAPolicyDeviceOwnerAuthenticationWithBiometrics;
+#if __clang_major__ >= 9 && MAC_OS_X_VERSION_MIN_REQUIRED >= 101500
         }
+#endif
 
         bool canAuthenticate = [context canEvaluatePolicy:policyCode error:nil];
         [context release];
@@ -274,11 +282,15 @@ bool TouchID::authenticate(const QString& message) const
         NSString* authMessage = msg.toNSString(); // autoreleased
 
         LAPolicy policyCode;
+#if __clang_major__ >= 9 && MAC_OS_X_VERSION_MIN_REQUIRED >= 101500
         if (@available(macOS 10.15, *)) {
             policyCode = LAPolicyDeviceOwnerAuthenticationWithBiometricsOrWatch;
         } else {
+#endif
             policyCode = LAPolicyDeviceOwnerAuthenticationWithBiometrics;
+#if __clang_major__ >= 9 && MAC_OS_X_VERSION_MIN_REQUIRED >= 101500
         }
+#endif
 
         [context evaluatePolicy:policyCode
                 localizedReason:authMessage reply:^(BOOL success, NSError* error) {