diff --git a/tools/tool-common.c b/tools/tool-common.c
index ee5099db..497a5097 100644
--- a/tools/tool-common.c
+++ b/tools/tool-common.c
@@ -40,7 +40,7 @@
 /* a hack to avoid having to depend on the static -util version of libdbus;
  * it's useful for ancillary programs to be able to use the shared library */
 void
-tool_millisleep (int ms)
+tool_millisleep (unsigned int ms)
 {
 #ifdef DBUS_WIN
   Sleep (ms);
diff --git a/tools/tool-common.h b/tools/tool-common.h
index c5984821..8659011c 100644
--- a/tools/tool-common.h
+++ b/tools/tool-common.h
@@ -32,7 +32,7 @@
 #define VERBOSE(...) do {} while (0)
 #endif
 
-void tool_millisleep (int ms);
+void tool_millisleep (unsigned int ms);
 void tool_oom (const char *doing) _DBUS_GNUC_NORETURN;
 dbus_bool_t tool_write_all (int fd, const void *buf, size_t size);