diff --git a/configure b/configure
index 5c616a9..c24db40 100755
--- a/configure
+++ b/configure
@@ -141,7 +141,7 @@ for var in prefix bindir mandir; do
 done
 
 # Check if is on Cygwin
-[ "$(expr substr $(uname -s) 1 10)" == "MINGW32_NT" ] && windows=y
+[ "$(expr substr "$(uname -s)" 1 10)" = "MINGW32_NT" ] && windows=y
 
 # If on MS-Windows, do not make the manpages.
 [ "$windows" ] && install_manpages=