diff --git a/packages/webpack-cli/lib/webpack-cli.js b/packages/webpack-cli/lib/webpack-cli.js
index d661a7cb865..52c9cc5e9e4 100644
--- a/packages/webpack-cli/lib/webpack-cli.js
+++ b/packages/webpack-cli/lib/webpack-cli.js
@@ -96,8 +96,6 @@ class WebpackCLI {
                 finalMode = configMode;
             } else if (NODE_ENV && (NODE_ENV === PRODUCTION || NODE_ENV === DEVELOPMENT)) {
                 finalMode = NODE_ENV;
-            } else {
-                finalMode = PRODUCTION;
             }
             return finalMode;
         };
@@ -177,10 +175,16 @@ class WebpackCLI {
             // Todo - handle multi config for all flags
             finalOptions.options = configOptions.map(() => ({ ...finalOptions.options }));
             configOptions.forEach((configObject, index) => {
-                finalOptions.options[index].mode = assignMode(mode, configObject);
+                const resolvedMode = assignMode(mode, configObject);
+                if (resolvedMode) {
+                    finalOptions.options[index].mode = resolvedMode;
+                }
             });
         } else {
-            finalOptions.options.mode = assignMode(mode, configOptions);
+            const resolvedMode = assignMode(mode, configOptions);
+            if (resolvedMode) {
+                finalOptions.options.mode = resolvedMode;
+            }
         }
         return finalOptions;
     }
diff --git a/test/mode/mode-single-arg/mode-single-arg.test.js b/test/mode/mode-single-arg/mode-single-arg.test.js
index c3577ac844c..d586c687049 100644
--- a/test/mode/mode-single-arg/mode-single-arg.test.js
+++ b/test/mode/mode-single-arg/mode-single-arg.test.js
@@ -2,12 +2,13 @@
 const { run } = require('../../utils/test-utils');
 
 describe('mode flags', () => {
-    it('should set mode=production by default', () => {
+    it('should not set mode=production by default', () => {
         const { stderr, stdout, exitCode } = run(__dirname);
 
         expect(exitCode).toBe(0);
         expect(stderr).toBeFalsy();
-        expect(stdout).toContain(`mode: 'production'`);
+        expect(stdout).not.toContain(`mode: 'production'`);
+        expect(stdout).toContain(`The 'mode' option has not been set, webpack will fallback to 'production' for this value.`);
     });
 
     it('should load a development config when --mode=development is passed', () => {