--- ./rtexif/rtexif.h.orig
+++ ./rtexif/rtexif.h
@@ -410,7 +410,7 @@
                 else
                 lensAperture = exp( log(a1)+(log(a2)-log(a1))/(log(f2)-log(f1))*(log(focalLength)-log(f1)) );
 
-                dif = abs(lensAperture - maxApertureAtFocal);
+                dif = std::abs(lensAperture - maxApertureAtFocal);
             }else
                 dif = 0;
             if( dif < deltaMin ){