diff --git a/src/rgbcx.h b/src/rgbcx.h
index 1321e55..90eb1c8 100644
--- a/src/rgbcx.h
+++ b/src/rgbcx.h
@@ -59,6 +59,7 @@
 #include <cstdint>
 #include <cstdlib>
 #include <cstring>
+#include <cmath>
 #include "tables.h"
 
 // By default, the table used to accelerate cluster fit on 4 color blocks uses a 969x128 entry table.