diff --git a/api/blocks/controller.go b/api/blocks/controller.go
index bd2482fda..5a537e615 100644
--- a/api/blocks/controller.go
+++ b/api/blocks/controller.go
@@ -40,6 +40,9 @@ func getObservedBlock(c *fiber.Ctx) error {
 	if err != nil {
 		return err
 	}
+	if result.Service == "" {
+		return c.JSON(nil)
+	}
 
 	return c.JSON(result)
 }
diff --git a/core/src/listener/api.ts b/core/src/listener/api.ts
index 539694e07..a021b1404 100644
--- a/core/src/listener/api.ts
+++ b/core/src/listener/api.ts
@@ -65,7 +65,7 @@ export async function getListener({
  * @return {Promise<IBlock>}
  * @exception {FailedToGetObservedBlock}
  */
-export async function getObservedBlock({ service }: { service: string }): Promise<IBlock> {
+export async function getObservedBlock({ service }: { service: string }): Promise<IBlock | null> {
   try {
     const endpoint = buildUrl(ORAKL_NETWORK_API_URL, `blocks/observed?service=${service}`)
     return (await axios.get(endpoint))?.data
diff --git a/core/src/listener/listener.ts b/core/src/listener/listener.ts
index 6ace84ee3..b64f05341 100644
--- a/core/src/listener/listener.ts
+++ b/core/src/listener/listener.ts
@@ -208,7 +208,7 @@ function latestJob({
 
     try {
       // We assume that observedBlock has been initialized in the db in state.add()
-      observedBlock = (await getObservedBlock({ service })).blockNumber
+      observedBlock = (await getObservedBlock({ service }))?.blockNumber as number
     } catch (e) {
       // Similarly to the failure during fetching the latest block
       // number, this error doesn't require job resubmission. The next
diff --git a/core/src/listener/state.ts b/core/src/listener/state.ts
index 6c9bede40..5a1584e06 100644
--- a/core/src/listener/state.ts
+++ b/core/src/listener/state.ts
@@ -194,9 +194,7 @@ export class State {
       await this.addBlockToHistoryQueue(contractAddress, block.blockNumber)
     }
 
-    // if there is no observedBlock record in the db,
-    // use the listenerInitType to determine how to initialize the listener
-    if (observedBlock.service === '') {
+    if (observedBlock == null) {
       switch (this.listenerInitType) {
         case 'clear':
         case 'latest':