diff -Naur a/configure.ac b/configure.ac
--- a/configure.ac	2019-05-04 10:38:57.000000000 +0000
+++ b/configure.ac	2019-09-12 01:47:01.000000000 +0000
@@ -669,6 +669,7 @@
 esac
 
 
+AM_CONDITIONAL([USE_PORTMIXER], [test "$use_portmixer" = yes])
 if [[ "$use_portmixer" = "yes" ]] ; then
    AC_DEFINE(USE_PORTMIXER, 1,
    [Define if PortMixer support should be enabled])
diff -Naur a/lib-src/Makefile.am b/lib-src/Makefile.am
--- a/lib-src/Makefile.am	2019-05-04 10:38:57.000000000 +0000
+++ b/lib-src/Makefile.am	2019-09-12 01:21:23.000000000 +0000
@@ -157,7 +157,9 @@
 endif
 
 # Note: portmixer needs to be linked against (the local or system) portaudio.
+if USE_PORTMIXER
 SUBDIRS += portmixer
+endif
 
 if USE_LOCAL_PORTSMF
 SUBDIRS += portsmf