diff --git a/src/bin/zfs-tpm-list.cpp b/src/bin/zfs-tpm-list.cpp
index b8b6562..baaaba6 100644
--- a/src/bin/zfs-tpm-list.cpp
+++ b/src/bin/zfs-tpm-list.cpp
@@ -12,7 +12,7 @@
 #define TZPFMS_BACKEND_MAX_LEN 16
 
 
-enum class key_loadedness : char {
+enum class key_loadedness : signed char {
 	none     = -1,
 	unloaded = 0,
 	loaded   = 1,