diff --git a/nsprpub/lib/libc/include/plvmx.h b/nsprpub/lib/libc/include/plvmx.h
new file mode 100644
index 000000000..5291e5dee
--- /dev/null
+++ b/nsprpub/lib/libc/include/plvmx.h
@@ -0,0 +1,27 @@
+#include <stdlib.h>
+#include <sys/types.h>
+
+/* In general, you should include "mozilla-config.h" or the equivalent
+   before including this file to choose the proper macro. */
+
+#ifndef _nspr_plvmx_h
+#define _nspr_plvmx_h
+
+#if TENFOURFOX_VMX
+
+#if defined (__cplusplus)
+extern "C" {
+#endif
+
+void *vmx_memchr(const void *b, int c, size_t len);
+
+#if defined (__cplusplus)
+}
+#endif
+
+#define VMX_MEMCHR vmx_memchr
+#else
+#define VMX_MEMCHR memchr
+#endif
+
+#endif