diff --git a/src/Diagram.ts b/src/Diagram.ts
index 7e6d24db6..4f1765899 100644
--- a/src/Diagram.ts
+++ b/src/Diagram.ts
@@ -2,6 +2,7 @@ import * as configApi from './config';
 import { log } from './logger';
 import { getDiagram } from './diagram-api/diagramAPI';
 import { detectType } from './diagram-api/detectType';
+import { isDetailedError } from './utils';
 export class Diagram {
   type = 'graph';
   parser;
@@ -42,11 +43,9 @@ export class Diagram {
       // Is this the correct way to access mermiad's parseError()
       // method ? (or global.mermaid.parseError()) ?
       if (parseError) {
-        // @ts-ignore
-        if (error.str != undefined) {
+        if (isDetailedError(error)) {
           // handle case where error string and hash were
           // wrapped in object like`const error = { str, hash };`
-          // @ts-ignore
           parseError(error.str, error.hash);
         } else {
           // assume it is just error string and pass it on
diff --git a/src/config.ts b/src/config.ts
index 20843ccbc..9eb688bb4 100644
--- a/src/config.ts
+++ b/src/config.ts
@@ -13,11 +13,11 @@ let currentConfig: MermaidConfig = assignWithDepth({}, defaultConfig);
 
 export const updateCurrentConfig = (siteCfg: MermaidConfig, _directives: any[]) => {
   // start with config being the siteConfig
-  let cfg = assignWithDepth({}, siteCfg);
+  let cfg: MermaidConfig = assignWithDepth({}, siteCfg);
   // let sCfg = assignWithDepth(defaultConfig, siteConfigDelta);
 
   // Join directives
-  let sumOfDirectives = {};
+  let sumOfDirectives: MermaidConfig = {};
   for (let i = 0; i < _directives.length; i++) {
     const d = _directives[i];
     sanitize(d);
@@ -28,16 +28,15 @@ export const updateCurrentConfig = (siteCfg: MermaidConfig, _directives: any[])
 
   cfg = assignWithDepth(cfg, sumOfDirectives);
 
-  // @ts-ignore
-  if (sumOfDirectives.theme && theme[sumOfDirectives.theme]) {
+  if (sumOfDirectives.theme && sumOfDirectives.theme in theme) {
     const tmpConfigFromInitialize = assignWithDepth({}, configFromInitialize);
     const themeVariables = assignWithDepth(
       tmpConfigFromInitialize.themeVariables || {},
-      // @ts-ignore
       sumOfDirectives.themeVariables
     );
-    // @ts-ignore
-    cfg.themeVariables = theme[cfg.theme].getThemeVariables(themeVariables);
+    if (cfg.theme && cfg.theme in theme) {
+      cfg.themeVariables = theme[cfg.theme as keyof typeof theme].getThemeVariables(themeVariables);
+    }
   }
 
   currentConfig = cfg;
diff --git a/src/diagrams/common/common.ts b/src/diagrams/common/common.ts
index 7421f48a2..057481768 100644
--- a/src/diagrams/common/common.ts
+++ b/src/diagrams/common/common.ts
@@ -147,7 +147,7 @@ export const evaluate = (val: string | boolean): boolean =>
 export const parseGenericTypes = function (text: string): string {
   let cleanedText = text;
 
-  if (text.indexOf('~') != -1) {
+  if (text.indexOf('~') !== -1) {
     cleanedText = cleanedText.replace('~', '<');
     cleanedText = cleanedText.replace('~', '>');
 
diff --git a/src/diagrams/git/gitGraphDetector.ts b/src/diagrams/git/gitGraphDetector.ts
index f5a660fc1..1c0a015e7 100644
--- a/src/diagrams/git/gitGraphDetector.ts
+++ b/src/diagrams/git/gitGraphDetector.ts
@@ -1,5 +1,5 @@
 import type { DiagramDetector } from '../../diagram-api/detectType';
 
 export const gitGraphDetector: DiagramDetector = (txt) => {
-  return txt.match(/^\s*gitGraph/) != null;
+  return txt.match(/^\s*gitGraph/) !== null;
 };
diff --git a/src/diagrams/mindmap/mindamapDetector.ts b/src/diagrams/mindmap/mindamapDetector.ts
index 18cf67312..42d6309ee 100644
--- a/src/diagrams/mindmap/mindamapDetector.ts
+++ b/src/diagrams/mindmap/mindamapDetector.ts
@@ -1,5 +1,5 @@
 import { DiagramDetector } from '../../diagram-api/detectType';
 
 export const mindmapDetector: DiagramDetector = (txt) => {
-  return txt.match(/^\s*mindmap/) != null;
+  return txt.match(/^\s*mindmap/) !== null;
 };
diff --git a/src/errorRenderer.ts b/src/errorRenderer.ts
index 1f2b61e2e..de0b31886 100644
--- a/src/errorRenderer.ts
+++ b/src/errorRenderer.ts
@@ -1,6 +1,7 @@
 /** Created by knut on 14-12-11. */
 import { select } from 'd3';
 import { log } from './logger';
+import { getErrorMessage } from './utils';
 
 let conf = {};
 
@@ -89,8 +90,7 @@ export const draw = (id: string, mermaidVersion: string) => {
     svg.attr('viewBox', '768 0 512 512');
   } catch (e) {
     log.error('Error while rendering info diagram');
-    // @ts-ignore
-    log.error(e.message);
+    log.error(getErrorMessage(e));
   }
 };
 
diff --git a/src/mermaid.ts b/src/mermaid.ts
index 95cf68c27..a46103f11 100644
--- a/src/mermaid.ts
+++ b/src/mermaid.ts
@@ -6,6 +6,7 @@ import { MermaidConfig } from './config.type';
 import { log } from './logger';
 import utils from './utils';
 import { mermaidAPI } from './mermaidAPI';
+import { isDetailedError } from './utils';
 
 /**
  * ## init
@@ -39,10 +40,10 @@ const init = function (
     initThrowsErrors(config, nodes, callback);
   } catch (e) {
     log.warn('Syntax Error rendering');
-    // @ts-ignore
-    log.warn(e.str);
+    if (isDetailedError(e)) {
+      log.warn(e.str);
+    }
     if (mermaid.parseError) {
-      // @ts-ignore
       mermaid.parseError(e);
     }
   }
@@ -56,6 +57,7 @@ const initThrowsErrors = function (
   const conf = mermaidAPI.getConfig();
   // console.log('Starting rendering diagrams (init) - mermaid.init', conf);
   if (config) {
+    // This is a legacy way of setting config. It is not documented and should be removed in the future.
     // @ts-ignore
     mermaid.sequenceConfig = config;
   }
diff --git a/src/utils.ts b/src/utils.ts
index 30ab57ad8..27c644ff0 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -933,6 +933,20 @@ export const sanitizeCss = (str) => {
   return str;
 };
 
+export interface DetailedError {
+  str: string;
+  hash: any;
+}
+
+export function isDetailedError(error: unknown): error is DetailedError {
+  return 'str' in error;
+}
+
+export function getErrorMessage(error: unknown): string {
+  if (error instanceof Error) return error.message;
+  return String(error);
+}
+
 export default {
   assignWithDepth,
   wrapLabel,