diff --git a/src/tilecache.cc b/src/tilecache.cc
index 80d5986..d042ee3 100644
--- a/src/tilecache.cc
+++ b/src/tilecache.cc
@@ -26,6 +26,7 @@
 #include <set>
 #include <list>
 #include <cassert>
+#include <cmath>
 
 #include <SDL2/SDL_surface.h>