diff --git a/src/components/App/index.tsx b/src/components/App/index.tsx
index f30ddc7c..962d72bd 100644
--- a/src/components/App/index.tsx
+++ b/src/components/App/index.tsx
@@ -56,8 +56,8 @@ export default class App extends Component<Props, State> {
     if (process.env.NODE_ENV === 'development') {
       this.setState(window.STATE);
       const oldCDU = this.componentDidUpdate;
-      this.componentDidUpdate = (props, state) => {
-        if (oldCDU) oldCDU.call(this, props, state);
+      this.componentDidUpdate = (props, state, prev) => {
+        if (oldCDU) oldCDU.call(this, props, state, prev);
         window.STATE = this.state;
       };
     }
diff --git a/src/components/Options/index.tsx b/src/components/Options/index.tsx
index 98783a07..5d2b1d31 100644
--- a/src/components/Options/index.tsx
+++ b/src/components/Options/index.tsx
@@ -40,7 +40,9 @@ import Checkbox from '../checkbox';
 import Expander from '../expander';
 import Select from '../select';
 
-const encoderOptionsComponentMap = {
+const encoderOptionsComponentMap: {
+  [x: string]: (new (...args: any[]) => Component<any, any>) | undefined;
+} = {
   [identity.type]: undefined,
   [optiPNG.type]: OptiPNGEncoderOptions,
   [mozJPEG.type]: MozJpegEncoderOptions,
diff --git a/src/components/compress/index.tsx b/src/components/compress/index.tsx
index af631030..2bb90f03 100644
--- a/src/components/compress/index.tsx
+++ b/src/components/compress/index.tsx
@@ -576,9 +576,9 @@ export default class Compress extends Component<Props, State> {
         mobileView={mobileView}
         preprocessorState={side.latestSettings.preprocessorState}
         encoderState={side.latestSettings.encoderState}
-        onEncoderTypeChange={this.onEncoderTypeChange.bind(this, index)}
-        onEncoderOptionsChange={this.onEncoderOptionsChange.bind(this, index)}
-        onPreprocessorOptionsChange={this.onPreprocessorOptionsChange.bind(this, index)}
+        onEncoderTypeChange={this.onEncoderTypeChange.bind(this, index as 0|1)}
+        onEncoderOptionsChange={this.onEncoderOptionsChange.bind(this, index as 0|1)}
+        onPreprocessorOptionsChange={this.onPreprocessorOptionsChange.bind(this, index as 0|1)}
       />
     ));
 
@@ -592,7 +592,7 @@ export default class Compress extends Component<Props, State> {
         source={source}
         loading={loading || side.loading}
         copyDirection={copyDirections[index]}
-        onCopyToOtherClick={this.onCopyToOtherClick.bind(this, index)}
+        onCopyToOtherClick={this.onCopyToOtherClick.bind(this, index as 0|1)}
         buttonPosition={mobileView ? 'stack-right' : buttonPositions[index]}
       >
         {!mobileView ? null : [