Add missing type definitions

1 files changed, 1 insertions, 1 deletions

diff --git a/packages/sol-cov/src/coverage_subprovider.ts b/packages/sol-cov/src/coverage_subprovider.ts
index b08291afb..08efeaa24 100644
--- a/packages/sol-cov/src/coverage_subprovider.ts
+++ b/packages/sol-cov/src/coverage_subprovider.ts
@@ -51,7 +51,7 @@ export class CoverageSubprovider extends Subprovider {
      * @param end Callback to call if subprovider handled the request and wants to pass back the request.
      */
     // tslint:disable-next-line:prefer-function-over-method async-suffix
-    public async handleRequest(payload: JSONRPCRequestPayload, next: NextCallback, end: ErrorCallback) {
+    public async handleRequest(payload: JSONRPCRequestPayload, next: NextCallback, end: ErrorCallback): Promise<void> {
         switch (payload.method) {
             case 'eth_sendTransaction':
                 const txData = payload.params[0];