diff --git a/src/shared/util.h b/src/shared/util.h
index bb2c10156..fa16d5252 100644
--- a/src/shared/util.h
+++ b/src/shared/util.h
@@ -45,9 +45,9 @@
 #include <sys/inotify.h>
 
 #if SIZEOF_PID_T == 4
-#  define PID_FMT "%" PRIu32
+#  define PID_FMT "%" PRIi32
 #elif SIZEOF_PID_T == 2
-#  define PID_FMT "%" PRIu16
+#  define PID_FMT "%" PRIi16
 #else
 #  error Unknown pid_t size
 #endif