diff -rupN doomsday-1.14.0/doomsday/config_unix.pri doomsday-1.14.0-new/doomsday/config_unix.pri
--- doomsday-1.14.0/doomsday/config_unix.pri	2014-04-16 14:13:44.000000000 +0300
+++ doomsday-1.14.0-new/doomsday/config_unix.pri	2015-08-24 22:55:01.113845969 +0300
@@ -41,7 +41,10 @@ DENG_PLUGIN_LIB_DIR = $$DENG_LIB_DIR/doo
 # the linker where to find them.
 !contains(DENG_LIB_DIR, ^/usr/.*): QMAKE_LFLAGS += -Wl,-rpath,$$DENG_LIB_DIR
 
-DENG_BASE_DIR = $$PREFIX/share/doomsday
+isEmpty(DENG_BASE_DIR) {
+    DENG_BASE_DIR = $$PREFIX/share/doomsday
+}
+
 DENG_DATA_DIR = $$DENG_BASE_DIR/data
 
 DEFINES += DENG_BASE_DIR=\"\\\"$${DENG_BASE_DIR}/\\\"\"