diff --git a/config.mk b/config.mk
index 0a55194..a370180 100644
--- a/config.mk
+++ b/config.mk
@@ -12,7 +12,7 @@ GTK_INC = $(shell pkg-config --cflags gtk+-2.0 poppler-glib)
 GTK_LIB = $(shell pkg-config --libs gtk+-2.0 gthread-2.0 poppler-glib)
 
 INCS = -I. -I/usr/include ${GTK_INC}
-LIBS = -lc ${GTK_LIB} -lpthread
+LIBS = -lc ${GTK_LIB} -lpthread -lm
 
 # flags
 CFLAGS += -std=c99 -pedantic -Wall -Wno-format-zero-length $(INCS)