diff -up gnome-panel-2.31.2/applets/clock/Makefile.am.libm gnome-panel-2.31.2/applets/clock/Makefile.am
--- gnome-panel-2.31.2/applets/clock/Makefile.am.libm	2010-06-17 10:21:14.000000000 +0200
+++ gnome-panel-2.31.2/applets/clock/Makefile.am	2010-06-17 10:21:28.000000000 +0200
@@ -67,7 +67,7 @@ CLOCK_LDADD =						\
 	$(CLOCK_LIBS)					\
 	$(LIBPANEL_APPLET_LIBS)				\
 	$(POLKIT_LIBS)				\
-	-lgweather
+	-lgweather -lm
 
 BUILT_SOURCES =					\
 	clock-marshallers.c			\