diff --git a/ANNOUNCE b/ANNOUNCE
index 69c1ff90deea947d11955867f71ef3c95aaafb7c..fe8d3c5d72fe4346355e52bd27b5e3fced05f74b 100644
--- a/ANNOUNCE
+++ b/ANNOUNCE
@@ -1,4 +1,4 @@
-Libpng 1.6.31beta02 - July 6, 2017
+Libpng 1.6.31beta02 - July 8, 2017
 
 This is not intended to be a public release. It will be replaced
 within a few weeks by a public version or by another test version.
@@ -69,8 +69,10 @@ Version 1.6.31beta01 [July 5, 2017]
   Added "Requires: zlib" to libpng.pc.in (Pieter Neerincx).
   Added special case for FreeBSD in arm/filter_neon.S (Maya Rashish).
 
-Version 1.6.31beta02 [July 6, 2017]
+Version 1.6.31beta02 [July 8, 2017]
   Added instructions for disabling hardware optimizations in INSTALL.
+  Added "--enable-hardware-optimizations" configuration flag to enable
+    or disable all hardware optimizations with one flag.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/CHANGES b/CHANGES
index 99301a6f53d03e9b55fe6ff0958e1ae76be7063b..8ba253f6e52c29d5269fa294c53cff1b74202b16 100644
--- a/CHANGES
+++ b/CHANGES
@@ -5864,8 +5864,10 @@ Version 1.6.31beta01 [July 5, 2017]
   Added "Requires: zlib" to libpng.pc.in (Pieter Neerincx).
   Added special case for FreeBSD in arm/filter_neon.S (Maya Rashish).
 
-Version 1.6.31beta02 [July 6, 2017]
+Version 1.6.31beta02 [July 8, 2017]
   Added instructions for disabling hardware optimizations in INSTALL.
+  Added "--enable-hardware-optimizations" configuration flag to enable
+    or disable all hardware optimizations with one flag.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/INSTALL b/INSTALL
index c527938b6657723a3b0b71c3e1d1283218fc52b8..14497f6d02e265d24eea8d89c153ddfa7c8ed26f 100644
--- a/INSTALL
+++ b/INSTALL
@@ -293,6 +293,10 @@ such as one of
    --enable-intel-sse=yes
    --enable-powerpc-vsx=yes
 
+or enable them all at once with
+
+   --enable-hardware-optimizations=yes
+
 or, if you are not using "configure", you can use one of
 
    CPPFLAGS += "-DPNG_ARM_NEON"
@@ -301,11 +305,15 @@ or, if you are not using "configure", you can use one of
    CPPFLAGS += "-DPNG_POWERPC_VSX"
 
 If you wish to avoid using them,
-you can disable them via configure options such as
+you can disable them via the configure option
+
+   --disable-hardware-optimizations
+
+to disable them all, or
 
-   --enable-arm-neon=no, --enable-mips-msa=no, --enable-intel-sse=no,
-   --enable-powerpc-vsx=no
+   --enable-intel-sse=no
 
+to disable a particular one,
 or via compiler-command options such as
 
    CPPFLAGS += "-DPNG_ARM_NEON_OPT=0, -DPNG_MIPS_MSA_OPT=0,
diff --git a/configure.ac b/configure.ac
index 9dceaabb62951aa293df92076d6f2ac24af04ad1..9024d99c72817cd2fc02594b949ac282cd21efca 100644
--- a/configure.ac
+++ b/configure.ac
@@ -300,6 +300,54 @@ AM_CONDITIONAL([DO_INSTALL_LIBPNG_CONFIG],
 # HOST SPECIFIC OPTIONS
 # =====================
 #
+# DEFAULT
+# =======
+#
+AC_ARG_ENABLE([hardware-optimizations],
+   AS_HELP_STRING([[[--enable-hardware-optimizations]]],
+      [Enable hardware optimizations: =no/off, yes/on:]),
+   [case "$enableval" in
+      no|off)
+         # disable hardware optimization on all systems:
+         enable_arm_neon=no
+         AC_DEFINE([PNG_ARM_NEON_OPT], [0],
+           [Disable ARM_NEON optimizations])
+         enable_mips_msa=no
+         AC_DEFINE([PNG_MIPS_MSA_OPT], [0],
+           [Disable MIPS_MSA optimizations])
+         enable_powerpc_vsx=no
+         AC_DEFINE([PNG_POWERPC_VSX_OPT], [0],
+           [Disable POWERPC VSX optimizations])
+         enable_intel_sse=no
+         AC_DEFINE([PNG_INTEL_SSE_OPT], [0],
+           [Disable INTEL_SSE optimizations])
+      *)
+         # allow enabling hardware optimization on any system:
+         case "$host_cpu" in
+            arm*|aarch64*)
+              enable_arm_neon=yes
+              AC_DEFINE([PNG_ARM_NEON_OPT], [0],
+                [Enable ARM_NEON optimizations])
+              ;;
+            mipsel*|mips64el*)
+              enable_mips_msa=yes
+              AC_DEFINE([PNG_MIPS_MSA_OPT], [0],
+                [Enable MIPS_MSA optimizations])
+              ;;
+            i?86|x86_64)
+              enable_intel_sse=yes
+              AC_DEFINE([PNG_INTEL_SSE_OPT], [1],
+                [Enable Intel SSE optimizations])
+              ;;
+            powerpc*|ppc64*)
+              enable_powerpc_vsx=yes
+              AC_DEFINE([PNG_POWERPC_VSX_OPT], [2],
+                [Enable POWERPC VSX optimizations])
+              ;;
+         esac
+         ;;
+   esac])
+
 # ARM
 # ===
 #