diff --git a/npa/configure.ac b/npa/configure.ac
index cbd145e..4ebf222 100644
--- a/npa/configure.ac
+++ b/npa/configure.ac
@@ -72,6 +72,7 @@ AC_TYPE_SIZE_T
 AC_TYPE_SSIZE_T
 AC_TYPE_UINT16_T
 AC_TYPE_UINT32_T
+AC_TYPE_UINT64_T
 AC_TYPE_UINT8_T
 
 # Checks for library functions.
diff --git a/npa/src/npa-tool.c b/npa/src/npa-tool.c
index f5a1984..5a8c847 100644
--- a/npa/src/npa-tool.c
+++ b/npa/src/npa-tool.c
@@ -343,8 +343,8 @@ main (int argc, char **argv)
     if (dobreak) {
         /* The biggest buffer sprintf could write with "%llu" */
         char secretbuf[strlen("18446744073709551615")+1];
-        unsigned long long secret = 0;
-        unsigned long long maxsecret = 0;
+        uint64_t secret = 0;
+        uint64_t maxsecret = 0;
 
         if (usepin) {
             pace_input.pin_id = PACE_PIN;