diff --git a/FL/math.h b/FL/math.h
index b78357e07..22c5e1a36 100644
--- a/FL/math.h
+++ b/FL/math.h
@@ -45,6 +45,10 @@
 inline double rint(double v) {return floor(v+.5);}
 inline double copysign(double a, double b) {return b<0 ? -a : a;}
 
+# elif defined(_AIX)
+
+inline long int lround(double v) {return (long int)round(v);}
+
 #  endif // (_WIN32 || CRAY) && !__MINGW32__
 
 #endif // !fl_math_h
diff --git a/src/Fl_Anim_GIF_Image.cxx b/src/Fl_Anim_GIF_Image.cxx
index 09e35095d..9d7e74949 100644
--- a/src/Fl_Anim_GIF_Image.cxx
+++ b/src/Fl_Anim_GIF_Image.cxx
@@ -22,7 +22,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <errno.h>
-#include <math.h> // lround()
+#include <FL/math.h> // lround()
 
 #include <FL/Fl_Anim_GIF_Image.H>