--- a/make/Jprt.gmk	Wed Jul 05 19:41:13 2017 +0200
+++ b/make/Jprt.gmk	Tue May 20 12:54:44 2014 +0200
@@ -23,8 +23,22 @@
 # questions.
 #
 
-# This file is contains targets utilities needed by JPRT.
+# This file contains targets and utilities needed by JPRT.
 
+# Cygpath is only defined when running on Cygwin
+ifneq ($(CYGPATH), )
+  # If we get JPRT_ARCHIVE_*BUNDLE externally, make sure they have /cygdrive
+  # style paths
+  ifdef JPRT_ARCHIVE_BUNDLE
+    override JPRT_ARCHIVE_BUNDLE := $(shell $(CYGPATH) -u $(JPRT_ARCHIVE_BUNDLE))
+  endif
+  ifdef JPRT_ARCHIVE_INSTALL_BUNDLE
+    override JPRT_ARCHIVE_INSTALL_BUNDLE := $(shell $(CYGPATH) -u $(JPRT_ARCHIVE_INSTALL_BUNDLE))
+  endif
+endif
+
+# When running in JPRT these will be provided. Need defaults so that this makefile
+# is valid anyway.
 ifndef JPRT_ARCHIVE_BUNDLE
   JPRT_ARCHIVE_BUNDLE=/tmp/jprt_bundles/j2sdk-image.zip
 endif