--- a/makefile
+++ b/makefile
@@ -23,11 +23,11 @@
 
 njplot : $(OBJECTS)
 	$(CC) -o njplot $(OBJECTS) \
-        -lvibrant -lncbi -lXm -lXt
+        -lvibrant -lncbi -lXm -lXt -lm
         
 unrooted : $(OBJUNROOTED)
 	$(CC) -o unrooted $(OBJUNROOTED) \
-        -lvibrant -lncbi -lXm -lXt
+        -lvibrant -lncbi -lXm -lXt -lm
 
 newicktops: njplot-vib.c
 	$(CC) -DNO_GUI  -DNO_PDF -o $@ njplot-vib.c -lm