diff --git a/make/ldlibpath.mk b/make/ldlibpath.mk
index 97d574c7..4ecd341e 100644
--- a/make/ldlibpath.mk
+++ b/make/ldlibpath.mk
@@ -2,7 +2,7 @@
 
 # -- LD_LIBRARY_PATH
 LD_LIBRARY_PATH_ENV          = $(shell echo $(FINAL_LDFLAGS) | $(SED) 's/^-[^L] *[^ ]*/ /g; s/[ 	]-[^L] *[^ ]*/ /g; s/-L[ ]*\([^ ]*\)[ ]*/\1:/g')
-ifndef JW_PKG_LD_LIBRARY_PATH
+ifeq ($(origin JW_PKG_LD_LIBRARY_PATH),undefined)
   JW_PKG_LD_LIBRARY_PATH    := $(call proj_query, ldlibpath $(PROJECT) $(PREREQ_BUILD))
 endif
 export LD_LIBRARY_PATH      := $(JW_PKG_LD_LIBRARY_PATH)
@@ -12,14 +12,14 @@ endif
 
 # -- PATH
 EXE_SEARCH_PATH_ENV         := $(PATH)
-ifndef JW_PKG_EXE_PATH
+ifeq ($(origin JW_PKG_EXE_PATH),undefined)
   JW_PKG_EXE_PATH           := $(call proj_query, exepath $(PROJECT) $(PREREQ_BUILD)):$(EXE_SEARCH_PATH_ENV)
 endif
 export PATH                 := $(JW_PKG_EXE_PATH)
 
 # -- PYTHONPATH
 PYTHONPATH_ENV              := $(PYTHONPATH)
-ifndef JW_PKG_PYTHON_PATH
+ifeq ($(origin JW_PKG_PYTHON_PATH),undefined)
   JW_PKG_PYTHON_PATH        := $(call proj_query, pythonpath $(PROJECT))
 endif
 export PYTHONPATH           := $(JW_PKG_PYTHON_PATH)