diff --git a/docs/tips/06-style-props-value-px.md b/docs/tips/06-style-props-value-px.md
index aeb2cb3e3f92a..3f308cbc69d43 100644
--- a/docs/tips/06-style-props-value-px.md
+++ b/docs/tips/06-style-props-value-px.md
@@ -18,11 +18,15 @@ See [Inline Styles](/react/tips/inline-styles.html) for more info.
 
 Sometimes you _do_ want to keep the CSS properties unitless. Here's a list of properties that won't get the automatic "px" suffix:
 
+- `boxFlex`
+- `boxFlexGroup`
 - `columnCount`
 - `fillOpacity`
 - `flex`
 - `flexGrow`
+- `flexPositive`
 - `flexShrink`
+- `flexNegative`
 - `fontWeight`
 - `lineClamp`
 - `lineHeight`
diff --git a/src/browser/ui/dom/CSSProperty.js b/src/browser/ui/dom/CSSProperty.js
index 05f764ba95c5f..f8e3c2624de1b 100644
--- a/src/browser/ui/dom/CSSProperty.js
+++ b/src/browser/ui/dom/CSSProperty.js
@@ -20,7 +20,9 @@ var isUnitlessNumber = {
   columnCount: true,
   flex: true,
   flexGrow: true,
+  flexPositive: true,
   flexShrink: true,
+  flexNegative: true,
   fontWeight: true,
   lineClamp: true,
   lineHeight: true,