diff --git a/Libraries/Experimental/FlatList.js b/Libraries/Experimental/FlatList.js
index c605d6b8b30..cf158fe0703 100644
--- a/Libraries/Experimental/FlatList.js
+++ b/Libraries/Experimental/FlatList.js
@@ -93,7 +93,7 @@ type OptionalProps = {
    * Multiple columns can only be rendered with horizontal={false} and will zig-zag like a flexWrap
    * layout. Items should all be the same height - masonry layouts are not supported.
    */
-  numColumns?: number,
+  numColumns: number,
   /**
    * Called once when the scroll position gets within onEndReachedThreshold of the rendered content.
    */
@@ -145,6 +145,7 @@ type Props = RequiredProps & OptionalProps; // plus props from the underlying im
 class FlatList extends React.PureComponent {
   static defaultProps = {
     keyExtractor: VirtualizedList.defaultProps.keyExtractor,
+    numColumns: 1,
     shouldItemUpdate: VirtualizedList.defaultProps.shouldItemUpdate,
   };
   props: Props;
@@ -194,13 +195,13 @@ class FlatList extends React.PureComponent {
   _captureRef = (ref) => { this._listRef = ref; };
 
   _checkProps(props: Props) {
-    const {getItem, getItemCount, horizontal, legacyImplementation, numColumns, } = props;
+    const {getItem, getItemCount, horizontal, legacyImplementation, numColumns} = props;
     invariant(!getItem && !getItemCount, 'FlatList does not support custom data formats.');
     if (numColumns > 1) {
       invariant(!horizontal, 'numColumns does not support horizontal.');
     }
     if (legacyImplementation) {
-      invariant(!(numColumns > 1), 'Legacy list does not support multiple columns.');
+      invariant(numColumns === 1, 'Legacy list does not support multiple columns.');
       // Warning: may not have full feature parity and is meant more for debugging and performance
       // comparison.
       if (!this._hasWarnedLegacy) {
@@ -228,7 +229,7 @@ class FlatList extends React.PureComponent {
   };
 
   _getItemCount = (data: Array<Item>): number => {
-    return Math.floor(data.length / (this.props.numColumns || 1));
+    return Math.floor(data.length / this.props.numColumns);
   };
 
   _keyExtractor = (items: Item | Array<Item>, index: number): string => {