diff --git a/ax_init_standard_project.m4 b/ax_init_standard_project.m4
index 1fa7db7..60f123d 100644
--- a/ax_init_standard_project.m4
+++ b/ax_init_standard_project.m4
@@ -405,7 +405,7 @@ AC_DEFUN([AX_PKG_REQUIRE], [
       PKG_REQUIREMENTS="${PKG_REQUIREMENTS}, m4_default([$2], [$1])"
     fi
   ], [
-    AC_MSG_WARN([Recommended package [m4_default([$2], [$1])] for feature $1 not installed])
+    AC_MSG_WARN([Recommended package m4_default([$2], [$1]) for feature $1 not installed])
     if test -n "$4"; then
       for pkg in $4; do
         PKG_CHECK_MODULES([$1], [$pkg], [