diff --git a/lib/utils/action-utils.js b/lib/utils/action-utils.js
--- a/lib/utils/action-utils.js
+++ b/lib/utils/action-utils.js
@@ -282,7 +282,7 @@
   ) => {
     const startingPayload = { ...inputStartingPayload, logInActionSource };
     dispatch(wrapActionPromise(actionTypes, promise, null, startingPayload));
-    return new Promise(r => (callServerEndpointCallback = r));
+    return new Promise<boolean>(r => (callServerEndpointCallback = r));
   };
   await resolveInvalidatedCookie(
     boundCallServerEndpoint,
@@ -340,7 +340,9 @@
       return Promise.resolve(null);
     }
     // Wait to run until we get our new cookie
-    return new Promise(r => serverEndpointCallsWaitingForNewCookie.push(r));
+    return new Promise<?CallServerEndpoint>(r =>
+      serverEndpointCallsWaitingForNewCookie.push(r),
+    );
   };
   // This function is a helper for the next function defined below
   const attemptToResolveInvalidation = async (
@@ -387,7 +389,9 @@
       return Promise.resolve(null);
     }
     if (currentlyWaitingForNewCookie) {
-      return new Promise(r => serverEndpointCallsWaitingForNewCookie.push(r));
+      return new Promise<?CallServerEndpoint>(r =>
+        serverEndpointCallsWaitingForNewCookie.push(r),
+      );
     }
     currentlyWaitingForNewCookie = true;
     return attemptToResolveInvalidation(sessionChange);
diff --git a/lib/utils/blob-service-upload.js b/lib/utils/blob-service-upload.js
--- a/lib/utils/blob-service-upload.js
+++ b/lib/utils/blob-service-upload.js
@@ -42,7 +42,7 @@
   }
 
   let failed = false;
-  const responsePromise = new Promise((resolve, reject) => {
+  const responsePromise = new Promise<void>((resolve, reject) => {
     xhr.onload = () => {
       if (failed) {
         return;
diff --git a/lib/utils/upload-blob.js b/lib/utils/upload-blob.js
--- a/lib/utils/upload-blob.js
+++ b/lib/utils/upload-blob.js
@@ -66,41 +66,43 @@
   }
 
   let failed = false;
-  const responsePromise = new Promise((resolve, reject) => {
-    xhr.onload = () => {
-      if (failed) {
-        return;
-      }
-      const text = xhr.responseText;
-      try {
-        resolve(JSON.parse(text));
-      } catch (e) {
-        console.log(text);
-        reject(e);
-      }
-    };
-    xhr.onabort = () => {
-      failed = true;
-      reject(new Error('request aborted'));
-    };
-    xhr.onerror = event => {
-      failed = true;
-      reject(event);
-    };
-    if (options && options.timeout) {
-      xhr.ontimeout = event => {
-        failed = true;
-        reject(event);
+  const responsePromise = new Promise<CallServerEndpointResponse>(
+    (resolve, reject) => {
+      xhr.onload = () => {
+        if (failed) {
+          return;
+        }
+        const text = xhr.responseText;
+        try {
+          resolve(JSON.parse(text));
+        } catch (e) {
+          console.log(text);
+          reject(e);
+        }
       };
-    }
-    if (options && options.abortHandler) {
-      options.abortHandler(() => {
+      xhr.onabort = () => {
         failed = true;
         reject(new Error('request aborted'));
-        xhr.abort();
-      });
-    }
-  });
+      };
+      xhr.onerror = event => {
+        failed = true;
+        reject(event);
+      };
+      if (options && options.timeout) {
+        xhr.ontimeout = event => {
+          failed = true;
+          reject(event);
+        };
+      }
+      if (options && options.abortHandler) {
+        options.abortHandler(() => {
+          failed = true;
+          reject(new Error('request aborted'));
+          xhr.abort();
+        });
+      }
+    },
+  );
 
   if (!failed) {
     xhr.send(formData);