diff --git a/acinclude.m4.in b/acinclude.m4.in
index da6cb55..12b8daa 100644
--- a/acinclude.m4.in
+++ b/acinclude.m4.in
@@ -6755,7 +6755,7 @@ AC_DEFUN([AC_PDF_GENERATION], [
     AC_CHECK_PROG(found_recode, recode, yes, no)
     AC_CHECK_PROG(found_html2ps, html2ps, yes, no)
     AC_CHECK_PROG(found_ps2pdf, ps2pdf, yes, no)
-    if test "x$found_recode" != "xyes" -o "x$found_html2ps" != "xyes" -o "x$found_ps2pdf" != "xyes"; then
+    if test "x$found_recode" != "xyes" && "x$found_html2ps" != "xyes" && "x$found_ps2pdf" != "xyes"; then
       if test "x$enable_pdfdocs" = "xyes"; then
         AC_MSG_ERROR(At least one of the tools for PDF generation is missing)
       fi