diff --git a/make/qt-defs.mk b/make/qt-defs.mk
index 71a55c36..f30f1cfe 100644
--- a/make/qt-defs.mk
+++ b/make/qt-defs.mk
@@ -6,16 +6,16 @@ QT_VERSION            ?= 4.3.0
 QT_MAJOR_VERSION      ?= $(shell echo $(QT_VERSION) | cut -d\. -f1)
 
 ifeq ($(QT_MAJOR_VERSION),2)
-	QT_PREFIX              = /usr/lib/qt2
+	QT_PREFIX             ?= /usr/lib/qt2
 	INCLUDE               += -I$(QT_PREFIX)/include
 else
 	ifeq ($(QT_MAJOR_VERSION),3)
-		QT_PREFIX      = /usr/lib/qt3
+		QT_PREFIX     ?= /usr/lib/qt3
 		INCLUDE       += -I$(QT_PREFIX)/include
 	else
 		ifeq ($(QT_MAJOR_VERSION),4)
-		#QT_PREFIX = $(HOME)/opt/qt4
-		QT_PREFIX  = /usr
+		#QT_PREFIX ?= $(HOME)/opt/qt4
+		QT_PREFIX  ?= /usr
 		INCLUDE += -I$(QT_PREFIX)/include \
 			$(addprefix -I$(QT_PREFIX)/include/, \
 			Qt Qt3Support QtAssistant QtCore QtDesigner \
@@ -37,26 +37,26 @@ else
 	endif
 endif
 
-MOC                    = $(QT_PREFIX)/bin/moc
-UIC                    = $(QT_PREFIX)/bin/uic
-RCC                    = $(QT_PREFIX)/bin/rcc
+MOC                   ?= $(QT_PREFIX)/bin/moc
+UIC                   ?= $(QT_PREFIX)/bin/uic
+RCC                   ?= $(QT_PREFIX)/bin/rcc
 
 UIFILES               += $(wildcard *.ui)
 RCCFILES              += $(wildcard *.qrc)
 
 ifneq ($(wildcard *.h),)
-MOC_H_HC               = $(shell grep -H Q_OBJECT $(wildcard *.h) | cut -d: -f1 | sort -u)
+MOC_H_HC              += $(shell grep -H Q_OBJECT $(wildcard *.h) | cut -d: -f1 | sort -u)
 endif
-MOC_H_UI               = $(patsubst %.ui,%.h,$(UIFILES))
-MOC_H                  = $(sort $(MOC_H_HC) $(MOC_H_UI))
-MOC_CPP                = $(patsubst %.h,moc_%.cpp,  $(MOC_H))
-RCC_CPP                = $(patsubst %.qrc,rcc_%.cpp, $(RCCFILES))
+MOC_H_UI              += $(patsubst %.ui,%.h,$(UIFILES))
+MOC_H                 += $(sort $(MOC_H_HC) $(MOC_H_UI))
+MOC_CPP               += $(patsubst %.h,moc_%.cpp,  $(MOC_H))
+RCC_CPP               += $(patsubst %.qrc,rcc_%.cpp, $(RCCFILES))
 ifeq ($(QT_MAJOR_VERSION),4)
-UIC_H                  = $(patsubst %.ui,ui_%.h,    $(UIFILES))
+UIC_H                 += $(patsubst %.ui,ui_%.h,    $(UIFILES))
 else
-UIC_H                  = $(patsubst %.ui,%.h,       $(UIFILES))
+UIC_H                 += $(patsubst %.ui,%.h,       $(UIFILES))
 endif
-UIC_CPP                = $(patsubst %.ui,uic_%.cpp, $(UIFILES))
+UIC_CPP               += $(patsubst %.ui,uic_%.cpp, $(UIFILES))
 
 OBJ                   += $(patsubst %.cpp,%.o,$(MOC_CPP))
 OBJ                   += $(patsubst %.cpp,%.o,$(UIC_CPP))