diff --git a/makefile.u b/makefile.u
index a1cb700..6d5fb78 100644
--- a/makefile.u
+++ b/makefile.u
@@ -88,7 +88,7 @@ libf2c.a: $(OFILES)
 ## arrange for $DYLD_LIBRARY_PATH to include the directory containing libf2c.so.
 
 libf2c.so: $(OFILES)
-	$(CC) $(LDFLAGS) -shared -o libf2c.so $(OFILES)
+	$(CC) $(LDFLAGS) -shared -Wl,-soname,libf2c.so.2 -o libf2c.so.2 -lm $(OFILES)
 
 ### If your system lacks ranlib, you don't need it; see README.