diff --git a/packages/angular/cli/models/schematic-command.ts b/packages/angular/cli/models/schematic-command.ts
index 15adbe941e31..11d272e7496a 100644
--- a/packages/angular/cli/models/schematic-command.ts
+++ b/packages/angular/cli/models/schematic-command.ts
@@ -128,8 +128,21 @@ export abstract class SchematicCommand extends Command {
 
     workflow.registry.addSmartDefaultProvider('projectName', (_schema: JsonObject) => {
       if (this._workspace) {
+        try {
         return this._workspace.getProjectByPath(normalize(process.cwd()))
                || this._workspace.getDefaultProjectName();
+        } catch (e) {
+          if (e instanceof experimental.workspace.AmbiguousProjectPathException) {
+            this.logger.warn(tags.oneLine`
+              Two or more projects are using identical roots.
+              Unable to determine project using current working directory.
+              Using default workspace project instead.
+            `);
+
+            return this._workspace.getDefaultProjectName();
+          }
+          throw e;
+        }
       }
 
       return undefined;
@@ -346,7 +359,7 @@ export abstract class SchematicCommand extends Command {
 
   private _cleanDefaults<T, K extends keyof T>(defaults: T, undefinedOptions: string[]): T {
     (Object.keys(defaults) as K[])
-      .filter(key => !undefinedOptions.map(strings.camelize).includes(key))
+      .filter(key => !undefinedOptions.map(strings.camelize).includes(key as string))
       .forEach(key => {
         delete defaults[key];
       });
diff --git a/packages/angular/cli/utilities/config.ts b/packages/angular/cli/utilities/config.ts
index 9e89aab50015..e17620818e11 100644
--- a/packages/angular/cli/utilities/config.ts
+++ b/packages/angular/cli/utilities/config.ts
@@ -140,11 +140,22 @@ export function validateWorkspace(json: JsonObject) {
   return true;
 }
 
+function getProjectByCwd(workspace: experimental.workspace.Workspace): string | null {
+  try {
+    return workspace.getProjectByPath(normalize(process.cwd()));
+  } catch (e) {
+    if (e instanceof experimental.workspace.AmbiguousProjectPathException) {
+      return workspace.getDefaultProjectName();
+    }
+    throw e;
+  }
+}
+
 export function getPackageManager(): string {
   let workspace = getWorkspace('local');
 
   if (workspace) {
-    const project = workspace.getProjectByPath(normalize(process.cwd()));
+    const project = getProjectByCwd(workspace);
     if (project && workspace.getProjectCli(project)) {
       const value = workspace.getProjectCli(project)['packageManager'];
       if (typeof value == 'string') {
@@ -258,7 +269,7 @@ export function getDefaultSchematicCollection(): string {
   let workspace = getWorkspace('local');
 
   if (workspace) {
-    const project = workspace.getProjectByPath(normalize(process.cwd()));
+    const project = getProjectByCwd(workspace);
     if (project && workspace.getProjectCli(project)) {
       const value = workspace.getProjectCli(project)['defaultCollection'];
       if (typeof value == 'string') {
@@ -319,7 +330,7 @@ export function getSchematicDefaults(
       }
     }
 
-    project = project || workspace.getProjectByPath(normalize(process.cwd()));
+    project = project || getProjectByCwd(workspace);
     if (project && workspace.getProjectSchematics(project)) {
       const schematicObject = workspace.getProjectSchematics(project)[fullName];
       if (schematicObject) {
@@ -339,7 +350,7 @@ export function isWarningEnabled(warning: string): boolean {
   let workspace = getWorkspace('local');
 
   if (workspace) {
-    const project = workspace.getProjectByPath(normalize(process.cwd()));
+    const project = getProjectByCwd(workspace);
     if (project && workspace.getProjectCli(project)) {
       const warnings = workspace.getProjectCli(project)['warnings'];
       if (typeof warnings == 'object' && !Array.isArray(warnings)) {
diff --git a/packages/angular_devkit/core/src/workspace/workspace.ts b/packages/angular_devkit/core/src/workspace/workspace.ts
index 09c4f5bc4689..d8964e6fa5f0 100644
--- a/packages/angular_devkit/core/src/workspace/workspace.ts
+++ b/packages/angular_devkit/core/src/workspace/workspace.ts
@@ -49,6 +49,11 @@ export class WorkspaceNotYetLoadedException extends BaseException {
   constructor() { super(`Workspace needs to be loaded before it is used.`); }
 }
 
+export class AmbiguousProjectPathException extends BaseException {
+  constructor(public readonly path: Path, public readonly projects: ReadonlyArray<string>) {
+    super(`Current active project is ambiguous (${projects.join(',')}) using path: '${path}'`);
+  }
+}
 
 export class Workspace {
   private readonly _workspaceSchemaPath = join(normalize(__dirname), 'workspace-schema.json');
@@ -175,11 +180,25 @@ export class Workspace {
       // the sort is stable and the first declared project will win).
       .sort((a, b) => b[0].length - a[0].length);
 
-    if (projects[0]) {
-      return projects[0][1];
+    if (projects.length === 0) {
+      return null;
+    } else if (projects.length > 1) {
+      const found = new Set<Path>();
+      const sameRoots = projects.filter(v => {
+        if (!found.has(v[0])) {
+          found.add(v[0]);
+
+          return false;
+        }
+
+        return true;
+      });
+      if (sameRoots.length > 0) {
+        throw new AmbiguousProjectPathException(path, sameRoots.map(v => v[1]));
+      }
     }
 
-    return null;
+    return projects[0][1];
   }
 
   getCli() {