Index: src/util/linewriter.h
===================================================================
--- src/util/linewriter.h
+++ src/util/linewriter.h
@@ -29,6 +29,7 @@
 #include <cmath>
 #include <cstring>
 #include <unistd.h>
+#include <stdint.h>
 
 /**
  * Custom buffered I/O writer for high performance and signal safety
@@ -148,14 +149,18 @@
         return true;
     }
 
-    inline static unsigned clz(unsigned V)
+    inline static unsigned clz(uint32_t V)
     {
         return __builtin_clz(V);
     }
 
-    inline static unsigned clz(long unsigned V)
+    inline static unsigned clz(uint64_t V)
     {
+    #if __SIZEOF_LONG__ == 8
         return __builtin_clzl(V);
+    #else
+        return __builtin_clzll(V);
+    #endif
     }
 
     template <typename V>