diff --git a/packages/popper/index.js.flow b/packages/popper/index.js.flow
new file mode 100644
index 0000000000..2b72f6468c
--- /dev/null
+++ b/packages/popper/index.js.flow
@@ -0,0 +1,142 @@
+declare module 'popper.js' {
+  declare type Position = 'top' | 'right' | 'bottom' | 'left';
+  declare type Placement =
+    | 'auto-start'
+    | 'auto'
+    | 'auto-end'
+    | 'top-start'
+    | 'top'
+    | 'top-end'
+    | 'right-start'
+    | 'right'
+    | 'right-end'
+    | 'bottom-end'
+    | 'bottom'
+    | 'bottom-start'
+    | 'left-end'
+    | 'left'
+    | 'left-start';
+
+  declare type Offset = {
+    top: number,
+    left: number,
+    width: number,
+    height: number,
+    position: Position,
+  };
+
+  declare type Boundary = 'scrollParent' | 'viewport' | 'window';
+
+  declare type Behavior = 'flip' | 'clockwise' | 'counterclockwise';
+
+  declare type Data = {
+    instance: Popper,
+    placement: Placement,
+    originalPlacement: Placement,
+    flipped: boolean,
+    hide: boolean,
+    arrowElement: Element,
+    styles: CSSStyleDeclaration,
+    arrowStyles: CSSStyleDeclaration,
+    boundaries: Object,
+    offsets: {
+      popper: Offset,
+      reference: Offset,
+      arrow: {
+        top: number,
+        left: number,
+      },
+    },
+  };
+
+  declare type ModifierFn = (data: Data, options: Object) => Data;
+
+  declare type BaseModifier = {
+    order?: number,
+    enabled?: boolean,
+    fn?: ModifierFn,
+  };
+
+  declare type Modifiers = {
+    shift?: BaseModifier,
+    offset?: BaseModifier & {
+      offset?: number | string,
+    },
+    preventOverflow?: BaseModifier & {
+      priority?: Position[],
+      padding?: number,
+      boundariesElement?: Boundary | Element,
+      escapeWithReference?: boolean,
+    },
+    keepTogether?: BaseModifier,
+    arrow?: BaseModifier & {
+      element?: string | Element | null,
+    },
+    flip?: BaseModifier & {
+      behavior?: Behavior | Position[],
+      padding?: number,
+      boundariesElement?: Boundary | Element,
+    },
+    inner?: BaseModifier,
+    hide?: BaseModifier,
+    applyStyle?: BaseModifier & {
+      onLoad?: Function,
+      gpuAcceleration?: boolean,
+    },
+    computeStyle?: BaseModifier & {
+      gpuAcceleration?: boolean,
+      x?: 'bottom' | 'top',
+      y?: 'left' | 'right',
+    },
+
+    [name: string]: (BaseModifier & { [string]: * }) | null,
+  };
+
+  declare type Options = {
+    placement?: Placement,
+    positionFixed?: boolean,
+    eventsEnabled?: boolean,
+    modifiers?: Modifiers,
+    removeOnDestroy?: boolean,
+
+    onCreate?: (data: Data) => void,
+
+    onUpdate?: (data: Data) => void,
+  };
+
+  declare var placements: Placement;
+
+  declare type ReferenceObject = {
+    +clientHeight: number,
+    +clientWidth: number,
+
+    getBoundingClientRect():
+      | ClientRect
+      | {
+          width: number,
+          height: number,
+          top: number,
+          right: number,
+          bottom: number,
+          left: number,
+        },
+  };
+
+  declare type Instance = {
+    destroy: () => void,
+    scheduleUpdate: () => void,
+    update: () => void,
+  };
+
+  declare class Popper {
+    static placements: Placement;
+
+    constructor(
+      reference: Element | ReferenceObject,
+      popper: Element,
+      options?: Options
+    ): Instance;
+  }
+
+  declare module.exports: Class<Popper>;
+}
diff --git a/packages/popper/package.json b/packages/popper/package.json
index d26bd64d7d..7104b7a844 100644
--- a/packages/popper/package.json
+++ b/packages/popper/package.json
@@ -32,7 +32,7 @@
     "postpublish": "nuget-publish && ./bower-publish.sh",
     "prebuild": "yarn lint",
     "pretest": "yarn lint",
-    "build": "node bundle.js",
+    "build": "node bundle.js && cp index.js.flow dist/esm/poppper.js.flow",
     "lint": "eslint .",
     "test": "popper-karma",
     "posttest": "tsc --project tests/types/tsconfig.json",
diff --git a/packages/tooltip/tests/functional/tooltip.js b/packages/tooltip/tests/functional/tooltip.js
index 5ecee409ed..5f1cf1a0f8 100644
--- a/packages/tooltip/tests/functional/tooltip.js
+++ b/packages/tooltip/tests/functional/tooltip.js
@@ -4,6 +4,7 @@ import then from '@popperjs/test-utils/utils/then.js';
 import '@popperjs/test-utils/utils/customEventPolyfill.js';
 
 const jasmineWrapper = document.getElementById('jasmineWrapper');
+const isIE10 = navigator.appVersion.indexOf('MSIE 10') !== -1;
 
 let reference;
 let instance;
@@ -299,7 +300,7 @@ describe('[tooltip.js]', () => {
           document.querySelector('.tooltip .tooltip-inner').textContent
         ).toBe(updatedContent);
         done();
-      })
+      });
     });
 
     it('should update title content with HTMLElement', done => {
@@ -316,14 +317,18 @@ describe('[tooltip.js]', () => {
       instance.updateTitleContent(el);
 
       then(() => {
-        expect(
-          document.querySelector('.tooltip-inner').innerHTML
-        ).toBe(el.outerHTML);
+        expect(document.querySelector('.tooltip-inner').innerHTML).toBe(
+          el.outerHTML
+        );
         done();
-      })
+      });
     });
 
     it('should update the tooltip position when changing the title', done => {
+      // Unreliable on IE...
+      if (isIE10) {
+        pending();
+      }
       const updatedContent = 'Updated string with a different length';
       instance = new Tooltip(reference, {
         title: 'Constructor message',
@@ -331,16 +336,20 @@ describe('[tooltip.js]', () => {
 
       instance.show();
 
-      const oldPosition = document.querySelector('.tooltip .tooltip-inner').getBoundingClientRect().left
+      const oldPosition = document
+        .querySelector('.tooltip .tooltip-inner')
+        .getBoundingClientRect().left;
 
       instance.updateTitleContent(updatedContent);
 
       then(() => {
         expect(
-          document.querySelector('.tooltip .tooltip-inner').getBoundingClientRect().left
+          document
+            .querySelector('.tooltip .tooltip-inner')
+            .getBoundingClientRect().left
         ).not.toBe(oldPosition);
         done();
-      }, 500)
+      }, 500);
     });
   });