diff --git a/dict-generate.cpp b/dict-generate.cpp
index 9fcc95d..94b20f4 100644
--- a/dict-generate.cpp
+++ b/dict-generate.cpp
@@ -890,7 +890,7 @@ void CreateArrays(NodeSPtr Root, StringIntSet_t & StrSet, StringOfInts & ChildAd
     if (x >= (1 << BITS_CHILD_MAP_INDEX))
     {
         char Tmp[24];
-        snprintf(Tmp, sizeof Tmp, "%lu", x);
+        snprintf(Tmp, sizeof Tmp, "%zu", x);
         throw string("Not enough bits for child map index value of ") + Tmp + " for " +
                 Its->s + " (BITS_CHILD_MAP_INDEX too small)";
     }