diff --git a/src/constants.ts b/src/constants.ts
index d6224c2..0551126 100644
--- a/src/constants.ts
+++ b/src/constants.ts
@@ -13,6 +13,8 @@ export const ERROR_CODE_MESSAGES: Record<ErrorCode, string> = {
     "Authorization required.  Find your API Key in the 'Local REST API' section of your Obsidian settings.",
   [ErrorCode.ContentTypeSpecificationRequired]:
     "Content-Type header required; this API accepts data in multiple content-types and you must indicate the content-type of your request body via the Content-Type header.",
+  [ErrorCode.InvalidContentType]:
+    "Unknown or invalid Content-Type specified in Content-Type header.",
   [ErrorCode.InvalidContentInsertionPositionValue]:
     "Invalid 'Content-Insertion-Position' header value.",
   [ErrorCode.InvalidContentForContentType]:
@@ -40,6 +42,9 @@ export const ERROR_CODE_MESSAGES: Record<ErrorCode, string> = {
     "The 'Operation' header you provided was invalid.",
   [ErrorCode.PatchFailed]:
     "The patch you provided could not be applied to the target content.",
+  [ErrorCode.InvalidSearch]: "The search query you provided is not valid.",
+  [ErrorCode.ErrorPreparingSimpleSearch]:
+    "Error encountered while calling Obsidian `prepareSimpleSearch` API.",
 };
 
 export enum ContentTypes {
diff --git a/src/requestHandler.ts b/src/requestHandler.ts
index 7e928f7..106183b 100644
--- a/src/requestHandler.ts
+++ b/src/requestHandler.ts
@@ -991,9 +991,24 @@ export default class RequestHandler {
     const results: SearchResponseItem[] = [];
 
     const query: string = req.query.query as string;
+    if (!(typeof query === "string")) {
+      return this.returnCannedResponse(res, {
+        message: "A single '?query=' parameter is required.",
+        errorCode: ErrorCode.InvalidSearch,
+      });
+    }
     const contextLength: number =
       parseInt(req.query.contextLength as string, 10) ?? 100;
-    const search = prepareSimpleSearch(query);
+    let search: ReturnType<typeof prepareSimpleSearch>;
+    try {
+      search = prepareSimpleSearch(query);
+    } catch (e) {
+      console.error("Could not prepare simple search: ", e);
+      return this.returnCannedResponse(res, {
+        message: `${e}`,
+        errorCode: ErrorCode.ErrorPreparingSimpleSearch,
+      });
+    }
 
     for (const file of this.app.vault.getMarkdownFiles()) {
       const cachedContents = await this.app.vault.cachedRead(file);
@@ -1099,11 +1114,16 @@ export default class RequestHandler {
     };
     const contentType = req.headers["content-type"];
 
-    if (!handlers[contentType]) {
+    if (!contentType) {
       this.returnCannedResponse(res, {
         errorCode: ErrorCode.ContentTypeSpecificationRequired,
       });
       return;
+    } else if (!handlers[contentType]) {
+      this.returnCannedResponse(res, {
+        errorCode: ErrorCode.InvalidContentType,
+      });
+      return;
     }
 
     try {
diff --git a/src/types.ts b/src/types.ts
index d62b315..f6e035d 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -5,6 +5,7 @@ import { IPeriodicNoteSettings } from "obsidian-daily-notes-interface";
 export enum ErrorCode {
   TextContentEncodingRequired = 40010,
   ContentTypeSpecificationRequired = 40011,
+  InvalidContentType = 40012,
   InvalidContentForContentType = 40015,
   InvalidContentInsertionPositionValue = 40050,
   MissingHeadingHeader = 40051,
@@ -17,10 +18,12 @@ export enum ErrorCode {
   PeriodIsNotEnabled = 40060,
   InvalidFilterQuery = 40070,
   PatchFailed = 40080,
+  InvalidSearch = 40090,
   ApiKeyAuthorizationRequired = 40101,
   PeriodDoesNotExist = 40460,
   PeriodicNoteDoesNotExist = 40461,
   RequestMethodValidOnlyForFiles = 40510,
+  ErrorPreparingSimpleSearch = 50010,
 }
 
 export interface LocalRestApiSettings {