diff -rupN pjproject-2.6/aconfigure.ac pjproject-2.6-new/aconfigure.ac
--- pjproject-2.6/aconfigure.ac	2017-01-25 12:23:08.000000000 +0100
+++ pjproject-2.6-new/aconfigure.ac	2017-09-01 18:52:24.843876152 +0200
@@ -5,12 +5,7 @@ host_orig="$host"
 AC_CANONICAL_BUILD
 AC_CANONICAL_HOST
 AC_CANONICAL_TARGET
-AC_CONFIG_HEADER([pjlib/include/pj/compat/os_auto.h
-		  pjlib/include/pj/compat/m_auto.h
-		  pjmedia/include/pjmedia/config_auto.h
-		  pjmedia/include/pjmedia-codec/config_auto.h
-		  pjsip/include/pjsip/sip_autoconf.h
-		 ])
+AC_CONFIG_HEADERS([pjlib/include/pj/compat/os_auto.h pjlib/include/pj/compat/m_auto.h pjmedia/include/pjmedia/config_auto.h pjmedia/include/pjmedia-codec/config_auto.h pjsip/include/pjsip/sip_autoconf.h])
 AC_CONFIG_FILES([build.mak 
 		 build/os-auto.mak 
 		 build/cc-auto.mak
@@ -1785,6 +1780,24 @@ AC_SUBST(ac_no_webrtc)
 AC_SUBST(ac_webrtc_instset)
 AC_SUBST(ac_webrtc_cflags)
 AC_SUBST(ac_webrtc_ldflags)
+
+AC_MSG_CHECKING(for available instruction set)
+AC_LINK_IFELSE([
+    AC_LANG_PROGRAM([[
+    #include <xmmintrin.h>
+    __m128 testfunc(float *a, float *b) {
+      return _mm_add_ps(_mm_loadu_ps(a), _mm_loadu_ps(b));
+    }
+  ]])],
+  [
+    instrset=sse2
+  ],
+  [
+    instrset=generic
+  ]
+)
+AC_MSG_RESULT($instrset)
+
 AC_ARG_ENABLE(libwebrtc,
 	      AS_HELP_STRING([--disable-libwebrtc],
 			     [Exclude libwebrtc in the build]),
@@ -1840,7 +1853,7 @@ AC_ARG_ENABLE(libwebrtc,
 			ac_webrtc_cflags="-msse2"
 			;;
 		     *win32* | *w32* | *darwin* | *linux*)
-			ac_webrtc_instset=sse2
+			ac_webrtc_instset=$instrset
 			;;
 		     *)
 			;;
diff -rupN pjproject-2.6/third_party/build/os-auto.mak.in pjproject-2.6-new/third_party/build/os-auto.mak.in
--- pjproject-2.6/third_party/build/os-auto.mak.in	2016-12-22 10:33:55.000000000 +0100
+++ pjproject-2.6-new/third_party/build/os-auto.mak.in	2017-09-01 18:52:24.846876150 +0200
@@ -104,8 +104,7 @@ else ifneq ($(findstring mips,@ac_webrtc
 else # Generic fixed point
     WEBRTC_SRC = \
 	      modules/audio_processing/aecm/aecm_core_c.o                \
-	      modules/audio_processing/ns/nsx_core_c.o                   \
-	      common_audio/signal_processing/complex_fft.o
+	      modules/audio_processing/ns/nsx_core_c.o
 endif
 endif
 endif
diff -rupN pjproject-2.6/third_party/webrtc/src/webrtc/modules/audio_processing/aec/aec_core.c pjproject-2.6-new/third_party/webrtc/src/webrtc/modules/audio_processing/aec/aec_core.c
--- pjproject-2.6/third_party/webrtc/src/webrtc/modules/audio_processing/aec/aec_core.c	2016-08-29 10:44:54.000000000 +0200
+++ pjproject-2.6-new/third_party/webrtc/src/webrtc/modules/audio_processing/aec/aec_core.c	2017-09-01 18:52:24.847876149 +0200
@@ -1478,7 +1478,7 @@ AecCore* WebRtcAec_CreateAec() {
   WebRtcAec_ComfortNoise = ComfortNoise;
   WebRtcAec_SubbandCoherence = SubbandCoherence;
 
-#if defined(WEBRTC_ARCH_X86_FAMILY)
+#if defined(WEBRTC_ARCH_X86_FAMILY) && defined(__SSE2__)
   if (WebRtc_GetCPUInfo(kSSE2)) {
     WebRtcAec_InitAec_SSE2();
   }
diff -rupN pjproject-2.6/third_party/webrtc/src/webrtc/modules/audio_processing/aec/aec_rdft.c pjproject-2.6-new/third_party/webrtc/src/webrtc/modules/audio_processing/aec/aec_rdft.c
--- pjproject-2.6/third_party/webrtc/src/webrtc/modules/audio_processing/aec/aec_rdft.c	2016-08-25 03:36:33.000000000 +0200
+++ pjproject-2.6-new/third_party/webrtc/src/webrtc/modules/audio_processing/aec/aec_rdft.c	2017-09-01 18:52:24.848876148 +0200
@@ -571,7 +571,7 @@ void aec_rdft_init(void) {
   cftfsub_128 = cftfsub_128_C;
   cftbsub_128 = cftbsub_128_C;
   bitrv2_128 = bitrv2_128_C;
-#if defined(WEBRTC_ARCH_X86_FAMILY)
+#if defined(WEBRTC_ARCH_X86_FAMILY) && defined(__SSE2__)
   if (WebRtc_GetCPUInfo(kSSE2)) {
     aec_rdft_init_sse2();
   }