diff --git a/include/strutils.h b/include/strutils.h
index e9f8a0c..2f6d285 100644
--- a/include/strutils.h
+++ b/include/strutils.h
@@ -16,6 +16,10 @@
 
 #include "c.h"
 
+// private, and clashing with libsystemd.
+#define parse_size ul__parse_size
+#define parse_range ul__parse_range
+
 /* initialize a custom exit code for all *_or_err functions */
 extern void strutils_set_exitcode(int exit_code);