diff --git a/configure.ac b/configure.ac
index 13526a9..83a06ed 100644
--- a/configure.ac
+++ b/configure.ac
@@ -119,10 +119,10 @@ if test "x$enable_libusb" = "xyes"; then
   if test x"$PKG_CONFIG" != "x"; then
     PKG_CHECK_MODULES([LIBUSB], [libusb], [WITH_USB=1], [WITH_USB=0])
     if test x"$WITH_USB" = "x1"; then
-    if test x"$PKG_CONFIG_REQUIRES" != x""; then
-      PKG_CONFIG_REQUIRES="$PKG_CONFIG_REQUIRES,"
-    fi
-    PKG_CONFIG_REQUIRES="$PKG_CONFIG_REQUIRES libusb"
+      if test x"$PKG_CONFIG_REQUIRES" != x""; then
+        PKG_CONFIG_REQUIRES="$PKG_CONFIG_REQUIRES,"
+      fi
+      PKG_CONFIG_REQUIRES="$PKG_CONFIG_REQUIRES libusb"
     fi
   fi