diff --git a/config.m4 b/config.m4
index b7515b2..4736498 100644
--- a/config.m4
+++ b/config.m4
@@ -13,6 +13,7 @@ dnl Make sure that the comment is aligned:
 if test "$PHP_PDLIB" != "no"; then
   PHP_REQUIRE_CXX()
   PHP_ADD_LIBRARY(stdc++, 1, PDLIB_SHARED_LIBADD)
+  PHP_ADD_LIBRARY(gif, 1, PDLIB_SHARED_LIBADD)
   PHP_SUBST(PDLIB_SHARED_LIBADD)
 
   pdlib_src_files="pdlib.cc \
@@ -65,4 +66,4 @@ AC_CONFIG_COMMANDS_POST([
   echo "Please submit bug reports at:"
   echo "  https://github.com/goodspb/pdlib/issues"
   echo ""
-])
\ No newline at end of file
+])