diff --git a/packages/gatsby-image/index.d.ts b/packages/gatsby-image/index.d.ts
index 8f7e934da6aeb..7a2d20af81fc1 100644
--- a/packages/gatsby-image/index.d.ts
+++ b/packages/gatsby-image/index.d.ts
@@ -30,6 +30,7 @@ interface GatsbyImageProps {
   fixed?: FixedObject | FixedObject[]
   fluid?: FluidObject | FluidObject[]
   fadeIn?: boolean
+  durationFadeIn?: number
   title?: string
   alt?: string
   className?: string | object
@@ -38,11 +39,12 @@ interface GatsbyImageProps {
   style?: object
   imgStyle?: object
   placeholderStyle?: object
+  placeholderClassName?: string
   backgroundColor?: string | boolean
   onLoad?: () => void
-  onStartLoad?: (param: { wasCached: boolean }) => void
   onError?: (event: any) => void
   onClick?: () => void
+  onStartLoad?: (param: { wasCached: boolean }) => void
   Tag?: string
   itemProp?: string
   loading?: `auto` | `lazy` | `eager`
diff --git a/packages/gatsby-image/src/index.js b/packages/gatsby-image/src/index.js
index faeae8520c8ed..cafc490bd9902 100644
--- a/packages/gatsby-image/src/index.js
+++ b/packages/gatsby-image/src/index.js
@@ -657,6 +657,10 @@ const fluidObject = PropTypes.shape({
   media: PropTypes.string,
 })
 
+// If you modify these propTypes, please don't forget to update following files as well:
+// https://github.com/gatsbyjs/gatsby/blob/master/packages/gatsby-image/index.d.ts
+// https://github.com/gatsbyjs/gatsby/blob/master/packages/gatsby-image/README.md#gatsby-image-props
+// https://github.com/gatsbyjs/gatsby/blob/master/docs/docs/gatsby-image.md#gatsby-image-props
 Image.propTypes = {
   resolutions: fixedObject,
   sizes: fluidObject,
diff --git a/packages/gatsby-image/src/withIEPolyfill/index.js b/packages/gatsby-image/src/withIEPolyfill/index.js
index 1bed0a73e5732..12eef5ec5b8f8 100644
--- a/packages/gatsby-image/src/withIEPolyfill/index.js
+++ b/packages/gatsby-image/src/withIEPolyfill/index.js
@@ -36,6 +36,10 @@ class ImageWithIEPolyfill extends Component {
   }
 }
 
+// If you modify these propTypes, please don't forget to update following files as well:
+// https://github.com/gatsbyjs/gatsby/blob/master/packages/gatsby-image/withIEPolyfill/index.d.ts
+// https://github.com/gatsbyjs/gatsby/blob/master/packages/gatsby-image/README.md#gatsby-image-props
+// https://github.com/gatsbyjs/gatsby/blob/master/docs/docs/gatsby-image.md#gatsby-image-props
 ImageWithIEPolyfill.propTypes = {
   objectFit: PropTypes.string,
   objectPosition: PropTypes.string,