diff --git a/package.json b/package.json
index 548ac820..9875fbde 100644
--- a/package.json
+++ b/package.json
@@ -31,8 +31,8 @@
         "posttest": "yarn lint",
         "prepack": "yarn build && oclif readme --multi",
         "pretest": "yarn format:check",
-        "test": "mocha test/*.ts \"src/**/*.test.ts\" && yarn workspace @devcycle/mcp-worker test",
-        "test:ci": "mocha --forbid-only test/*.ts \"src/**/*.test.ts\" && yarn workspace @devcycle/mcp-worker test",
+        "test": "mocha -r ts-node/register test/*.ts \"src/**/*.test.ts\" && yarn workspace @devcycle/mcp-worker test",
+        "test:ci": "mocha --forbid-only -r ts-node/register test/*.ts \"src/**/*.test.ts\" && yarn workspace @devcycle/mcp-worker test",
         "test:update-snapshots": "UPDATE_SNAPSHOT=1 yarn test",
         "version": "oclif readme --multi && git add README.md"
     },
diff --git a/src/mcp/tools/selfTargetingTools.ts b/src/mcp/tools/selfTargetingTools.ts
index 03490da9..6e21c56e 100644
--- a/src/mcp/tools/selfTargetingTools.ts
+++ b/src/mcp/tools/selfTargetingTools.ts
@@ -54,7 +54,11 @@ export async function updateSelfTargetingIdentityHandler(
             return await handleZodiosValidationErrors(
                 () =>
                     updateUserProfile(authToken, projectKey, {
-                        dvcUserId: args.dvc_user_id,
+                        dvcUserId:
+                            typeof args.dvc_user_id === 'string' &&
+                            args.dvc_user_id.trim() === ''
+                                ? null
+                                : args.dvc_user_id,
                     }),
                 'updateUserProfile',
             )
diff --git a/src/mcp/types.ts b/src/mcp/types.ts
index f670aca5..23c95fda 100644
--- a/src/mcp/types.ts
+++ b/src/mcp/types.ts
@@ -402,7 +402,6 @@ export const UpdateFeatureStatusArgsSchema = z.object({
 export const UpdateSelfTargetingIdentityArgsSchema = z.object({
     dvc_user_id: z
         .string()
-        .nullable()
         .describe(
             'DevCycle User ID for self-targeting (use null or empty string to clear)',
         ),
diff --git a/src/mcp/utils/api.test.ts b/src/mcp/utils/api.test.ts
index 1b343180..d853b1c9 100644
--- a/src/mcp/utils/api.test.ts
+++ b/src/mcp/utils/api.test.ts
@@ -34,12 +34,11 @@ describe('DevCycleApiClient', () => {
 
             // Create a proper mock Zodios error with data property
             class ZodiosValidationError extends Error {
-                constructor(
-                    message: string,
-                    public data: any,
-                ) {
+                public data: unknown
+                constructor(message: string, data: unknown) {
                     super(message)
                     this.name = 'ZodiosValidationError'
+                    this.data = data
                 }
             }