diff --git a/.eslintrc.js b/.eslintrc.js
index 6c58a645..626868ca 100644
--- a/.eslintrc.js
+++ b/.eslintrc.js
@@ -10,6 +10,9 @@ module.exports = {
     // Tweak rules set by airbnb config
     // We need to allow use of console.log for verbose mode
     'no-console': 'off',
+    // airbnb config forbids optionalDependencies
+    // https://github.com/airbnb/javascript/blob/c5bee75b1b358a3749f1a6d38ee6fad73de28e29/packages/eslint-config-airbnb-base/rules/imports.js#L95
+    "import/no-extraneous-dependencies": [ "error", { "optionalDependencies": true }]
   },
   overrides: [
     {
diff --git a/lib/transports/httpTransport.js b/lib/transports/httpTransport.js
index 07fdaf95..72cc4d21 100644
--- a/lib/transports/httpTransport.js
+++ b/lib/transports/httpTransport.js
@@ -17,7 +17,7 @@
 
 const http = require('http');
 
-const httpCall = (config, xmlInput, done) => {
+function httpCall(config, xmlInput, done) {
   const {
     database = '*LOCAL',
     username = null,
@@ -85,6 +85,6 @@ const httpCall = (config, xmlInput, done) => {
   });
   request.write(queryString);
   request.end();
-};
+}
 
 exports.httpCall = httpCall;
diff --git a/lib/transports/idbTransport.js b/lib/transports/idbTransport.js
index 979fec24..e421a458 100644
--- a/lib/transports/idbTransport.js
+++ b/lib/transports/idbTransport.js
@@ -15,15 +15,18 @@
 // DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
-const idbCall = (config, xmlInput, cb) => {
-  const {
-    dbconn, dbstmt, IN, CLOB, CHAR, SQL_ATTR_DBC_SYS_NAMING, SQL_FALSE,
-    // idb-connector is an optional dependency, since users may not use this transport
-    // thus we can't globally require it
-    // eslint-disable-next-line max-len
-    // eslint-disable-next-line global-require, import/no-extraneous-dependencies, import/no-unresolved
-  } = require('idb-connector');
+let idb = null;
+
+try {
+  // eslint-disable-next-line global-require
+  idb = require('idb-connector');
+} catch (e) {
+  if (e.code !== 'MODULE_NOT_FOUND') {
+    throw e;
+  }
+}
 
+function idbCall(config, xmlInput, cb) {
   const {
     database = '*LOCAL',
     username = null,
@@ -37,9 +40,9 @@ const idbCall = (config, xmlInput, cb) => {
   let xmlOutput = '';
   const sql = `call ${xslib}.iPLUGR512K(?,?,?)`;
   // eslint-disable-next-line new-cap
-  const conn = new dbconn();
+  const conn = new idb.dbconn();
 
-  conn.setConnAttr(SQL_ATTR_DBC_SYS_NAMING, SQL_FALSE);
+  conn.setConnAttr(idb.SQL_ATTR_DBC_SYS_NAMING, idb.SQL_FALSE);
 
   if (typeof verbose === 'boolean') {
     conn.debug(verbose);
@@ -56,12 +59,12 @@ const idbCall = (config, xmlInput, cb) => {
     return;
   }
   // eslint-disable-next-line new-cap
-  const stmt = new dbstmt(conn);
+  const stmt = new idb.dbstmt(conn);
 
   const parameters = [
-    [ipc, IN, CHAR],
-    [ctl, IN, CHAR],
-    [xmlInput, IN, CLOB],
+    [ipc, idb.IN, idb.CHAR],
+    [ctl, idb.IN, idb.CHAR],
+    [xmlInput, idb.IN, idb.CLOB],
   ];
 
   // Before returning to caller, we must clean up
@@ -109,6 +112,6 @@ const idbCall = (config, xmlInput, cb) => {
       });
     });
   });
-};
+}
 
 exports.idbCall = idbCall;
diff --git a/lib/transports/odbcTransport.js b/lib/transports/odbcTransport.js
index b5592727..7786a9f4 100644
--- a/lib/transports/odbcTransport.js
+++ b/lib/transports/odbcTransport.js
@@ -15,11 +15,18 @@
 // DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
-function odbcCall(config, xmlInput, done) {
-  // odbc is an optional dependency, since users may not use this transport
-  // eslint-disable-next-line global-require, import/no-extraneous-dependencies
-  const odbc = require('odbc');
+let odbc = null;
 
+try {
+  // eslint-disable-next-line global-require
+  odbc = require('odbc');
+} catch (e) {
+  if (e.code !== 'MODULE_NOT_FOUND') {
+    throw e;
+  }
+}
+
+function odbcCall(config, xmlInput, done) {
   const {
     host = 'localhost',
     username = null,
diff --git a/lib/transports/sshTransport.js b/lib/transports/sshTransport.js
index 243e264e..450feaf1 100644
--- a/lib/transports/sshTransport.js
+++ b/lib/transports/sshTransport.js
@@ -15,11 +15,9 @@
 // DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
-function sshCall(config, xmlIn, done) {
-  // ssh2 is an optional dependency, since users may not use this transport
-  // eslint-disable-next-line global-require, import/no-extraneous-dependencies
-  const { Client } = require('ssh2');
+const { Client } = require('ssh2');
 
+function sshCall(config, xmlIn, done) {
   const {
     verbose = false,
   } = config;