diff --git a/make/defs.mk b/make/defs.mk
index 451c6f0e..d22a60d3 100644
--- a/make/defs.mk
+++ b/make/defs.mk
@@ -90,7 +90,12 @@ ALL_CPP     = $(LOCAL_CPP) $(PREREQ_CPP)
 ALL_CSRC    = $(LOCAL_CSRC) $(PREREQ_CSRC)
 
 TEXTCLEAN   = $(wildcard *~ .*~ .*.swp *.rep)
-INCLUDE     = -I. -I$(TOPDIR)/include -I$(MODDIR)/include $(PROJECT_INCLUDE) $(LOCAL_INCLUDE)
+
+INCLUDE     = -I. -I$(TOPDIR)/include $(PROJECT_INCLUDE) $(LOCAL_INCLUDE)
+
+ifneq ($(TOPDIR),$(MODDIR))
+INCLUDE    += -I$(MODDIR)/include
+endif
 
 ifndef INSTALL_LIBDIR
 INSTALL_LIBDIR = $(PREFIX)/lib