diff --git a/kpdf/QOutputDev.cpp b/kpdf/QOutputDev.cpp
index c823bdf66..896ae97b4 100644
--- a/kpdf/QOutputDev.cpp
+++ b/kpdf/QOutputDev.cpp
@@ -18,6 +18,7 @@
 #include <unistd.h>
 #include <string.h>
 #include <ctype.h>
+#include <math.h>
 #include <iostream>
 
 // include xpdf config.h file