diff --git a/packages/@angular/cli/commands/config.ts b/packages/@angular/cli/commands/config.ts
index e83740e590..70eb8b24af 100644
--- a/packages/@angular/cli/commands/config.ts
+++ b/packages/@angular/cli/commands/config.ts
@@ -20,6 +20,13 @@ export interface ConfigOptions {
   global?: boolean;
 }
 
+const validCliPaths = new Map([
+  ['cli.warnings.versionMismatch', 'boolean'],
+  ['cli.warnings.typescriptMismatch', 'boolean'],
+  ['cli.defaultCollection', 'string'],
+  ['cli.packageManager', 'string'],
+]);
+
 /**
  * Splits a JSON path string into fragments. Fragments can be used to get the value referenced
  * by the path. For example, a path of "a[3].foo.bar[2]" would give you a fragment array of
@@ -157,12 +164,28 @@ export default class ConfigCommand extends Command {
   }
 
   private set(options: ConfigOptions) {
+    if (!options.jsonPath || !options.jsonPath.trim()) {
+      throw new Error('Invalid Path.');
+    }
+    if (options.global
+        && !options.jsonPath.startsWith('schematics.')
+        && !validCliPaths.has(options.jsonPath)) {
+      throw new Error('Invalid Path.');
+    }
+
     const [config, configPath] = getWorkspaceRaw(options.global ? 'global' : 'local');
 
     // TODO: Modify & save without destroying comments
     const configValue = config.value;
 
     const value = parseJson(options.value, JsonParseMode.Loose);
+    const pathType = validCliPaths.get(options.jsonPath);
+    if (pathType) {
+      if (typeof value != pathType) {
+        throw new Error(`Invalid value type; expected a ${pathType}.`);
+      }
+    }
+
     const result = setValueFromPath(configValue, options.jsonPath, value);
 
     if (result === undefined) {
@@ -176,7 +199,7 @@ export default class ConfigCommand extends Command {
       throw new SilentError();
     }
 
-    const output = JSON.stringify(configValue);
+    const output = JSON.stringify(configValue, null, 2);
     writeFileSync(configPath, output);
   }
 
diff --git a/tests/e2e/tests/commands/config/config-global.ts b/tests/e2e/tests/commands/config/config-global.ts
index d4443cb964..d351404441 100644
--- a/tests/e2e/tests/commands/config/config-global.ts
+++ b/tests/e2e/tests/commands/config/config-global.ts
@@ -25,6 +25,7 @@ export default function() {
         throw new Error(`Expected "true", received "${JSON.stringify(stdout)}".`);
       }
     })
-    .then(() => ng('config', '--global', 'schematics.@schematics/angular.component.inlineStyle', 'false'))
+    .then(() => expectToFail(() => ng('config', '--global', 'cli.warnings.notreal', 'true')))
+    .then(() => ng('config', '--global', 'cli.warnings.versionMismatch', 'false'))
     .then(() => expectFileToExist(path.join(homedir(), '.angular.json')));
 }