diff --git a/mkspecs/features/common_pre.prf b/mkspecs/features/common_pre.prf
index 75a3bea19..da544f1a6 100644
--- a/mkspecs/features/common_pre.prf
+++ b/mkspecs/features/common_pre.prf
@@ -130,12 +130,6 @@ equals(WORD_SIZE,64)|!win32: disableSwiftConfig(sims.fsx, sims.fs9)
 
 linux-g++: QMAKE_LFLAGS_DEBUG *= -rdynamic
 
-################################
-# Suppress stupid warnings
-################################
-
-include(warnings.pri)
-
 ################################
 # Handle addresses larger than 2GB
 ################################
@@ -144,12 +138,27 @@ equals(WORD_SIZE,32) {
     win32-g++: QMAKE_LFLAGS *= -Wl,--large-address-aware
 }
 
+################################
+# Support different clang drivers
+################################
+
+defineReplace(clangArg) {
+    clang_cl: return(/clang:$$1)
+    else: return($$1)
+}
+
 ################################
 # Externals
 ################################
 
 include(externals.pri)
 
+################################
+# Enable useful warnings, disable stupid ones
+################################
+
+include(warnings.pri)
+
 ################################
 # Includes
 ################################
diff --git a/mkspecs/features/externals.pri b/mkspecs/features/externals.pri
index f32c54196..5745c0fd2 100644
--- a/mkspecs/features/externals.pri
+++ b/mkspecs/features/externals.pri
@@ -39,6 +39,10 @@ else {
     QMAKE_CXXFLAGS += -idirafter $$EXTERNALSROOT/common/include
 }
 
+llvm {
+    QMAKE_CXXFLAGS_WARN_ON *= $$clangArg(-isystem$$system_path($$EXTERNALSROOT/common/include))
+}
+
 equals(WORD_SIZE,64) {
     EXTERNALS_BIN_DIR = $$EXTERNALSROOT/$$EXTERNALS_SPEC/64/bin
     EXTERNALS_LIB_DIR = $$EXTERNALSROOT/$$EXTERNALS_SPEC/64/lib
diff --git a/mkspecs/features/libraries.pri b/mkspecs/features/libraries.pri
index bd7c012a2..1674d8f9c 100644
--- a/mkspecs/features/libraries.pri
+++ b/mkspecs/features/libraries.pri
@@ -29,12 +29,15 @@ fsuipc {
 simconnect {
     DEFINES += SIMCONNECT_H_NOMANIFEST
     equals(WORD_SIZE,64) {
-        INCLUDEPATH *= $$EXTERNALSROOT/common/include/simconnect/P3D-v4
+        SIMCONNECT_INCLUDE += $$EXTERNALSROOT/common/include/simconnect/P3D-v4
         DEFINES += P3D_SDK_VERSION=400
     }
     equals(WORD_SIZE,32) {
-        INCLUDEPATH *= $$EXTERNALSROOT/common/include/simconnect/FSX-XPack
+        SIMCONNECT_INCLUDE += $$EXTERNALSROOT/common/include/simconnect/FSX-XPack
     }
+    INCLUDEPATH *= $$SIMCONNECT_INCLUDE
+    gcc:QMAKE_CXXFLAGS_WARN_ON += -isystem $$SIMCONNECT_INCLUDE
+    llvm:QMAKE_CXXFLAGS_WARN_ON *= $$clangArg(-isystem$$system_path($$SIMCONNECT_INCLUDE))
 }
 
 blackgui {
diff --git a/mkspecs/features/warnings.pri b/mkspecs/features/warnings.pri
index 221b322f5..3a6187e8e 100644
--- a/mkspecs/features/warnings.pri
+++ b/mkspecs/features/warnings.pri
@@ -6,13 +6,16 @@ msvc:QMAKE_CXXFLAGS_WARN_ON -= -w44996
 clang_cl:QMAKE_CXXFLAGS_WARN_ON *= /W4 -Wno-unknown-pragmas -Wno-undefined-inline -Wno-self-assign-overloaded
 gcc:QMAKE_CXXFLAGS_WARN_ON *= -Woverloaded-virtual
 gcc:QMAKE_CXXFLAGS_USE_PRECOMPILE = -Winvalid-pch $$QMAKE_CXXFLAGS_USE_PRECOMPILE
+gcc|llvm:QMAKE_CXXFLAGS_WARN_ON *= -Wzero-as-null-pointer-constant
+gcc:QMAKE_CXXFLAGS_WARN_ON += -isystem $$[QT_INSTALL_HEADERS]/QtCore
+llvm:QMAKE_CXXFLAGS_WARN_ON *= -Wno-system-headers
 
 # elevated warnings
 swiftConfig(allowNoisyWarnings) {
     llvm {
         QMAKE_CXXFLAGS_WARN_ON -= -Wno-self-assign-overloaded
-        QMAKE_CXXFLAGS_WARN_ON *= -Weverything --system-header-prefix=$$[QT_INSTALL_HEADERS]
-        QMAKE_CXXFLAGS_WARN_ON += -Wno-system-headers -Wno-c++98-compat-pedantic -Wno-class-varargs -Wno-covered-switch-default
+        QMAKE_CXXFLAGS_WARN_ON *= -Weverything $$clangArg(--system-header-prefix=$$[QT_INSTALL_HEADERS])
+        QMAKE_CXXFLAGS_WARN_ON += -Wno-c++98-compat-pedantic -Wno-class-varargs -Wno-covered-switch-default
         QMAKE_CXXFLAGS_WARN_ON += -Wno-documentation -Wno-documentation-unknown-command -Wno-double-promotion -Wno-exit-time-destructors
         QMAKE_CXXFLAGS_WARN_ON += -Wno-gnu -Wno-missing-prototypes -Wno-newline-eof -Wno-padded -Wno-undefined-reinterpret-cast
         QMAKE_CXXFLAGS_WARN_ON += -Wno-unused-macros -Wno-used-but-marked-unused -Wno-weak-template-vtables
diff --git a/src/blackgui/blackgui.pro b/src/blackgui/blackgui.pro
index 9b454e1ea..06d1e0a38 100644
--- a/src/blackgui/blackgui.pro
+++ b/src/blackgui/blackgui.pro
@@ -25,6 +25,10 @@ else {
     QMAKE_CXXFLAGS += -idirafter $$EXTERNALSROOT/common/include/qwt
 }
 
+llvm {
+    QMAKE_CXXFLAGS_WARN_ON *= $$clangArg(-isystem$$system_path($$EXTERNALSROOT/common/include/qwt))
+}
+
 # needed for "ShellScalingApi.h" only
 # win32 { LIBS *= -lSHCore }