diff --git a/autoconf/m4/opengl.m4 b/autoconf/m4/opengl.m4
index bc6187698b..95db3dbdfb 100644
--- a/autoconf/m4/opengl.m4
+++ b/autoconf/m4/opengl.m4
@@ -14,7 +14,7 @@ AC_DEFUN([SM_X_WITH_OPENGL],
 	    XLIBS="-L$x_libraries"
 	fi
 
-	XLIBS +="-lX11"
+	XLIBS+="-lX11"
 
 	if test -n "$x_includes"; then
 	    # See if we can compile X applications without using $XCFLAGS.