diff --git a/configure.ac b/configure.ac
index 88157c3e2e..d7e3cb5da9 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1151,7 +1151,7 @@ AC_CHECK_HEADERS([netdb.h netinet/in.h arpa/inet.h])
 
 ## Darwin
 AC_SUBST([H5_IS_DARWIN])
-H5_IS_DARWIN="no
+H5_IS_DARWIN="no"
 case $host_os in
   darwin*)
     AC_DEFINE([HAVE_DARWIN], [1], [Define if Darwin or Mac OS X])