--- a/browser/app/profile/extensions/Makefile.in
+++ b/browser/app/profile/extensions/Makefile.in
@@ -53,17 +53,17 @@ EXTENSIONS = \
   testpilot@labs.mozilla.com \
   $(NULL)
 
 define _INSTALL_EXTENSION
 $(NSINSTALL) -D $(dir) && \
   $(PYTHON) $(MOZILLA_DIR)/config/Preprocessor.py $(DEFINES) $(ACDEFINES) $(srcdir)/$(dir)/install.rdf.in > $(dir)/install.rdf && \
   cd $(dir) && \
   $(ZIP) -r9XD $(DISTROEXT)/$(dir).xpi install.rdf && \
-  cd $(srcdir)/$(dir) && \
+  cd $(call core_abspath,$(srcdir)/$(dir)) && \
   $(ZIP) -r9XD $(DISTROEXT)/$(dir).xpi * -x install.rdf.in
 
 endef # do not remove the blank line!
 
 libs::
 	$(NSINSTALL) -D $(DISTROEXT)
 	$(foreach dir,$(EXTENSIONS),$(_INSTALL_EXTENSION))
 endif