diff --git a/configure.ac b/configure.ac
index 2711840ddbdd772d023bdc4427b005df4c579a7c..00fb9a55686bfeda837590f32c16103201c21497 100644
--- a/configure.ac
+++ b/configure.ac
@@ -842,7 +842,8 @@ FP_COMPARE_VERSIONS([$fp_cv_sphinx_version],-lt,1.0.0,
     [AC_MSG_WARN([Sphinx version 1.0.0 or later is required to build documentation]); SPHINXBUILD=;])
 if test -n "$SPHINXBUILD"; then
   if "$SPHINXBUILD" -b text utils/check-sphinx utils/check-sphinx/dist > /dev/null 2>&1; then true; else
-    AC_MSG_ERROR([Sphinx for python3 is required to build documentation.])
+    AC_MSG_WARN([Sphinx for python3 is required to build documentation.])
+    SPHINXBUILD=;
   fi
 fi