diff --git a/.travis.yml b/.travis.yml
index 14c278520..427efb37d 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -9,7 +9,7 @@ matrix:
     env:
     - CC_OVERRIDE=gcc
     - ENABLE_SIG_PICNIC=0
-    - USE_OPENSSL=1
+    - WITH_OPENSSL=1
     - CHECK_STYLE=true
     addons:
       apt:
@@ -67,7 +67,7 @@ matrix:
     compiler: gcc
     env:
     - CC_OVERRIDE=gcc-6
-    - USE_OPENSSL=1
+    - WITH_OPENSSL=1
     addons:
       apt:
         sources:
@@ -84,8 +84,7 @@ matrix:
     env:
     - CC_OVERRIDE=clang
     - AES_NI=0
-    - USE_OPENSSL=1
-    - OPENSSL_DIR=/usr/local/opt/openssl # openssl is a keg-only package
+    - WITH_OPENSSL=1
     before_install:
     - brew update
     - brew install doxygen graphviz
diff --git a/.travis/all-tests.sh b/.travis/all-tests.sh
index d4659d1d2..f035b69b8 100755
--- a/.travis/all-tests.sh
+++ b/.travis/all-tests.sh
@@ -33,11 +33,10 @@ source $(dirname $0)/defs.sh
 	# construct configure arguments
 	enable_disable_str=
 
-	if [[ ${USE_OPENSSL} == 1 ]];then
-		enable_disable_str=" --enable-openssl"
-		if [[ ! -z "${OPENSSL_DIR// }" ]];then
-			enable_disable_str+=" --with-openssl-dir=${OPENSSL_DIR}"
-		fi
+	if [[ ${WITH_OPENSSL} == 1 ]];then
+		enable_disable_str=" --with-openssl"
+	else
+		enable_disable_str=" --without-openssl"
 	fi
 
 	if [[ ${AES_NI} == 0 ]];then
diff --git a/README.md b/README.md
index 07b28d807..1f5b9b779 100644
--- a/README.md
+++ b/README.md
@@ -134,7 +134,7 @@ Run the build system:
 
 (If on macOS you encounter an error like `Can't exec "libtoolize": No such file or directory at ...`, try running with `LIBTOOLIZE=glibtoolize autoreconf -i`.)
 
-You can enable/disable various algorithms at compile-time, tell liboqs to use OpenSSL for certain crypto algorithms, and more; see `./configure --help`.  (In particular, on macOS, you might want to point liboqs to brew's version of OpenSSL, via the command: `./configure --enable-openssl --with-openssl-dir=/usr/local/opt/openssl`.)
+You can enable/disable various algorithms at compile-time, tell liboqs to use OpenSSL for certain crypto algorithms, and more; see `./configure --help`.
 
 ### Build results
 
diff --git a/config/external-libraries.m4 b/config/external-libraries.m4
index aef11cb2e..bef37fab7 100644
--- a/config/external-libraries.m4
+++ b/config/external-libraries.m4
@@ -1,17 +1,49 @@
 # Checks for libraries.
-AC_DEFUN([ADD_EXTERNAL_LIB],
-  [AC_ARG_WITH(
-    [openssl-dir],
-    AS_HELP_STRING([--with-openssl-dir=dir],[openssl dir used locally (default /usr).]),
-    [AC_DEFINE_UNQUOTED(OPENSSLDIR, [$withval], [OPENSSL DIR used locally])
-     AC_SUBST(OPENSSL_DIR, [$withval])],
-    [AC_SUBST(OPENSSL_DIR, /usr)]
-  )]
-  [AC_ARG_WITH(
-    [m4ri-dir],
-    AS_HELP_STRING([--with-m4ri-dir=dir],[m4ri dir used locally (default /usr).]),
-    [AC_DEFINE_UNQUOTED(M4RIDIR, [$withval], [M4RI DIR used locally])
-     AC_SUBST(M4RI_DIR, [$withval])],
+AC_DEFUN([ADD_EXTERNAL_LIB],[
+
+  AC_MSG_CHECKING([whether to use OpenSSL])
+  # define the --with-openssl option
+  AC_ARG_WITH([openssl],
+    [AS_HELP_STRING(
+      [--without-openssl],
+      [disable OpenSSL; use --with-openssl=dir to specify OpenSSL dir (default /usr or /usr/local/opt/openssl on macOS)]
+    )],
+    [with_openssl=$withval],
+    [with_openssl=default]
+  )
+  # platform-specific default directory
+  AS_IF(
+    [test "x${with_openssl}" = "xdefault"],
+    [AM_COND_IF(ON_DARWIN,
+      [with_openssl=/usr/local/opt/openssl],
+      [with_openssl=/usr]
+    )]
+  )
+  AS_IF(
+    [test "x${with_openssl}" = "xno"],
+    [AC_MSG_RESULT([no])],
+    [
+      AC_MSG_RESULT([${with_openssl}])
+      # set OPENSSL_DIR based on value provided
+      AC_SUBST([OPENSSL_DIR], [${with_openssl}])
+    ]
+  )
+  # define automake conditional USE_OPENSSL
+  AM_CONDITIONAL(USE_OPENSSL, [test "x${with_openssl}" != "xno"])
+  # define C macro USE_OPENSSL
+  AM_COND_IF(USE_OPENSSL,
+    [AC_DEFINE(USE_OPENSSL, 1, [Defined to 1 if using OpenSSL in liboqs])]
+  )
+
+  AC_ARG_WITH([m4ri-dir],
+    [AS_HELP_STRING(
+      [--with-m4ri-dir=dir],
+      [m4ri dir used locally (default /usr)]
+    )],
+    [
+      AC_DEFINE_UNQUOTED(M4RIDIR, [$withval], [M4RI DIR used locally])
+      AC_SUBST(M4RI_DIR, [$withval])
+    ],
     [AC_SUBST(M4RI_DIR, /usr)]
-  )]
-)
+  )
+])
diff --git a/config/features.m4 b/config/features.m4
index e78f18192..82822e8b7 100644
--- a/config/features.m4
+++ b/config/features.m4
@@ -23,7 +23,7 @@ AC_DEFUN([ARG_ENABL_SET_WRAP],
 AC_DEFUN([CONFIG_FEATURE_FLAGS],
 [
 
-  #The flags are organizes according to features then cryptosystems.
+  # The flags are organized according to features then cryptosystems.
 
   # The parameters are
   # 1) Flag-name
@@ -31,7 +31,6 @@ AC_DEFUN([CONFIG_FEATURE_FLAGS],
   # 3) Compilation param name
   # 4) Compilation directory
   ARG_DISBL_SET_WRAP([aes-ni],  [aes_ni],  [USE_AES_NI])
-  ARG_ENABL_SET_WRAP([openssl], [openssl], [USE_OPENSSL])
 
   AS_IF([test "x${enable_shared}" = "xyes" ], AC_MSG_RESULT([yes]), AC_MSG_RESULT([no]))
   AM_CONDITIONAL([ENABLE_SHARED],[test "x${enable_shared}" = "xyes"])
@@ -53,11 +52,8 @@ AC_DEFUN([CONFIG_FEATURE_FLAGS],
 ##### OQS_COPY_FROM_PQCLEAN_FRAGMENT_ARG_DISBL_SET_WRAP_END
   ARG_DISBL_SET_WRAP([kem-frodokem], [kem_frodokem], [ENABLE_KEM_FRODOKEM], [src/kem/frodokem])
   ARG_DISBL_SET_WRAP([kem-sike],  [kem_sike],  [ENABLE_KEM_SIKE],  [src/kem/sike])
-
-  ARG_DISBL_SET_WRAP([sig-picnic], [sig_picnic],
-                     [ENABLE_SIG_PICNIC], [src/sig/picnic])
-  ARG_DISBL_SET_WRAP([sig-qtesla], [sig_qtesla],
-                     [ENABLE_SIG_QTESLA], [src/sig/qtesla])
+  ARG_DISBL_SET_WRAP([sig-picnic], [sig_picnic], [ENABLE_SIG_PICNIC], [src/sig/picnic])
+  ARG_DISBL_SET_WRAP([sig-qtesla], [sig_qtesla], [ENABLE_SIG_QTESLA], [src/sig/qtesla])
 ]
 )
 
diff --git a/configure.ac b/configure.ac
index a1725e360..505cde746 100644
--- a/configure.ac
+++ b/configure.ac
@@ -25,6 +25,9 @@ AC_DEFINE([OQS_MASTER_BRANCH],[],[liboqs branch])
 AC_CONFIG_HEADERS([config.h])
 AC_CONFIG_MACRO_DIRS([config])
 
+# Detect the host CPU and x86 features that are available.
+DETECT_HOST_AND_CPU
+
 # Set paths to external libraries.
 ADD_EXTERNAL_LIB
 
@@ -42,9 +45,6 @@ AC_GENERAL_CHECKS
 # DOXYGEN SUPPORT
 CONFIG_DOXYGEN
 
-# Detect the host CPU and x86 features that are availble.
-DETECT_HOST_AND_CPU
-
 # Configure the list of supported features
 CONFIG_FEATURES
 
diff --git a/scripts/arm-cross-compile.sh b/scripts/arm-cross-compile.sh
index ebf7d5704..c18c30120 100755
--- a/scripts/arm-cross-compile.sh
+++ b/scripts/arm-cross-compile.sh
@@ -30,6 +30,6 @@ hacks=(
 	CFLAGS=-D_ARM_		# Several files aren't using the right define
 )
 
-./configure --disable-shared --enable-static --host="${CHOST}" --build="$CBUILD" CC="${CHOST}-gcc" --with-openssl-dir="${PREFIX}" "${hacks[@]}"
+./configure --disable-shared --enable-static --host="${CHOST}" --build="$CBUILD" CC="${CHOST}-gcc" --with-openssl="${PREFIX}" "${hacks[@]}"
 make -j
 make -j check LDFLAGS="-L${PREFIX}/lib -static"