diff --git a/configure.ac b/configure.ac
index 3115504e2..ffb504b08 100644
--- a/configure.ac
+++ b/configure.ac
@@ -749,6 +749,7 @@ case "${host}" in
 	so="dll"
 	if test "x$je_cv_msvc" = "xyes" ; then
 	  importlib="lib"
+	  JE_APPEND_VS(CPPFLAGS, -DJEMALLOC_NO_PRIVATE_NAMESPACE)
 	  DSO_LDFLAGS="-LD"
 	  EXTRA_LDFLAGS="-link -DEBUG"
 	  CTARGET='-Fo$@'