diff --git a/build.pri b/build.pri
index b56c2dcd4..86952bb18 100644
--- a/build.pri
+++ b/build.pri
@@ -27,3 +27,45 @@ else {
     VER_PAT           = $${BLACK_VER_PAT}
     VERSION           = $${BLACK_VERSION}
 }
+
+###########################
+# Detect 32 or 64 bits
+###########################
+
+win32-msvc* {
+    win32:contains(QMAKE_TARGET.arch, x86_64) {
+        WORD_SIZE = 64
+    }
+    else {
+        WORD_SIZE = 32
+    }
+}
+win32-g++ {
+    WIN_FIND = $$(SYSTEMROOT)\system32\find
+    MINGW64 = $$system($$QMAKE_CXX -Q --help=target | $$WIN_FIND \"-m64\")
+    contains(MINGW64,[enabled]) {
+        WORD_SIZE = 64
+    }
+    else {
+        WORD_SIZE = 32
+    }
+}
+linux-g++ {
+    GCC64 = $$system($$QMAKE_CXX -Q --help=target | grep m64)
+    contains(MINGW64,[enabled]) {
+        WORD_SIZE = 64
+    }
+    else {
+        WORD_SIZE = 32
+    }
+}
+linux-g++-32 {
+    WORD_SIZE = 32
+}
+linux-g++-64 {
+    WORD_SIZE = 64
+}
+macx-clang {
+    # TODO
+    WORD_SIZE = 64
+}
diff --git a/externals.pri b/externals.pri
index 31fdeafdb..5d0a5add4 100644
--- a/externals.pri
+++ b/externals.pri
@@ -24,56 +24,26 @@ isEmpty(EXTERNALDIR) {
 INCLUDEPATH *= $$EXTERNALDIR/include
 
 # and the library path depending on the used compiler
-
 win32-msvc2010 {
-    win32:contains(QMAKE_TARGET.arch, x86_64) {
-        LIBS *= -L$$EXTERNALDIR/vs2010_64/lib
-    }
-    win32:contains(QMAKE_TARGET.arch, x86) {
-        LIBS *= -L$$EXTERNALDIR/vs2010_32/lib
-        LIBS += -luser32
-    }
+    equals(WORD_SIZE,64): LIBS *= -L$$EXTERNALDIR/vs2010_64/lib
+    equals(WORD_SIZE,32): LIBS *= -L$$EXTERNALDIR/vs2010_32/lib
+    equals(WORD_SIZE,32): LIBS += -luser32
 }
 win32-msvc2013 {
-    win32:contains(QMAKE_TARGET.arch, x86_64) {
-        LIBS *= -L$$EXTERNALDIR/vs2013_64/lib
-    }
-    win32:contains(QMAKE_TARGET.arch, x86) {
-        LIBS *= -L$$EXTERNALDIR/vs2013_32/lib
-        LIBS += -luser32
-    }
+    equals(WORD_SIZE,64): LIBS *= -L$$EXTERNALDIR/vs2013_64/lib
+    equals(WORD_SIZE,32): LIBS *= -L$$EXTERNALDIR/vs2013_32/lib
+    equals(WORD_SIZE,32): LIBS += -luser32
 }
-
 win32-g++ {
-    WIN_FIND = $$(SYSTEMROOT)\system32\find
-    MINGW64 = $$system($$QMAKE_CXX -Q --help=target | $$WIN_FIND \"-m64\")
-    contains(MINGW64,[enabled]) {
-        LIBS *= -L$$EXTERNALDIR/mingw64/lib
-    }
-    else {
-        LIBS *= -L$$EXTERNALDIR/mingw32/lib
-    }
+    equals(WORD_SIZE,64): LIBS *= -L$$EXTERNALDIR/mingw64/lib
+    equals(WORD_SIZE,32): LIBS *= -L$$EXTERNALDIR/mingw32/lib
     LIBS += -luser32
 }
-
-linux-g++ {
-    GCC64 = $$system($$QMAKE_CXX -Q --help=target | grep m64)
-    contains(GCC64,[enabled]) {
-        LIBS *= -L$$EXTERNALDIR/linux64/lib
-    }
-    else {
-        LIBS *= -L$$EXTERNALDIR/linux32/lib
-    }
+linux-g++* {
+    equals(WORD_SIZE,64): LIBS *= -L$$EXTERNALDIR/linux64/lib
+    equals(WORD_SIZE,32): LIBS *= -L$$EXTERNALDIR/linux32/lib
 }
-
-linux-g++-32 {
-    LIBS *= -L$$EXTERNALDIR/linux32/lib
-}
-
-linux-g++-64 {
-    LIBS *= -L$$EXTERNALDIR/linux64/lib
-}
-
 macx-clang {
-    LIBS *= -L$$EXTERNALDIR/macx-clang64/lib
+    equals(WORD_SIZE,64): LIBS *= -L$$EXTERNALDIR/macx-clang64/lib
+    equals(WORD_SIZE,32): LIBS *= -L$$EXTERNALDIR/macx-clang32/lib
 }
diff --git a/src/xbus/xbus.pro b/src/xbus/xbus.pro
index 25fe137a3..2d231b97e 100644
--- a/src/xbus/xbus.pro
+++ b/src/xbus/xbus.pro
@@ -27,46 +27,17 @@ linux:DEFINES += LIN
 macx:DEFINES += APL
 
 # X-Plane plugins must follow a prescribed filename and directory structure.
-# CPU architecture detection copied from externals.pri;
-# TODO: refactor so detection is is done in only one place.
 TARGET_EXT = .xpl
 win32:TARGET = win
 linux:TARGET = lin
 macx:TARGET = mac
-win32:contains(QMAKE_TARGET.arch, x86_64) {
-    DESTDIR = ../../xbus/64
-}
-win32:contains(QMAKE_TARGET.arch, x86) {
-    DESTDIR = ../../xbus
-}
-win32-g++ {
-    WIN_FIND = $$(SYSTEMROOT)\system32\find
-    MINGW64 = $$system($$QMAKE_CXX -Q --help=target | $$WIN_FIND \"-m64\")
-    contains(MINGW64,[enabled]) {
-        DESTDIR = ../../xbus/64
-    }
-    else {
-        DESTDIR = ../../xbus
-    }
-}
-linux-g++ {
-    GCC64 = $$system($$QMAKE_CXX -Q --help=target | grep m64)
-    contains(GCC64,[enabled]) {
-        DESTDIR = ../../xbus/64
-    }
-    else {
-        DESTDIR = ../../xbus
-    }
-}
-linux-g++-64 {
-    DESTDIR = ../../xbus/64
-}
-linux-g++-32 {
-    DESTDIR = ../../xbus
-}
 macx {
     # a single dylib file contains both 32bit and 64bit binaries
     DESTDIR = ../../xbus
 }
+else {
+    equals(WORD_SIZE,64): DESTDIR = ../../xbus/64
+    equals(WORD_SIZE,32): DESTDIR = ../../xbus
+}
 
 include (../../libraries.pri)