diff --git a/src/lib/prompts.ts b/src/lib/prompts.ts
index 453c8d60..9b36f91c 100644
--- a/src/lib/prompts.ts
+++ b/src/lib/prompts.ts
@@ -122,7 +122,7 @@ export function getChoicesForCommitPrompt(
       name = `${position}${message} ${pullStatus}`;
     }
 
-    const short = c.sourcePullRequest
+    const short = c.sourcePullRequest?.mergeCommit
       ? `#${c.sourcePullRequest.number} (${getShortSha(
           c.sourcePullRequest.mergeCommit.sha,
         )})`
diff --git a/src/lib/sourceCommit/getPullRequestStates.ts b/src/lib/sourceCommit/getPullRequestStates.ts
index 2d6acad8..119d9a8f 100644
--- a/src/lib/sourceCommit/getPullRequestStates.ts
+++ b/src/lib/sourceCommit/getPullRequestStates.ts
@@ -93,10 +93,12 @@ export function getPullRequestStates({
         state: 'MERGED' as const,
         url: sourcePullRequest.url,
         number: sourcePullRequest.number,
-        mergeCommit: {
-          message: sourcePullRequest.mergeCommit.message,
-          sha: sourcePullRequest.mergeCommit.sha,
-        },
+        mergeCommit: sourcePullRequest.mergeCommit
+          ? {
+              message: sourcePullRequest.mergeCommit.message,
+              sha: sourcePullRequest.mergeCommit.sha,
+            }
+          : undefined,
       };
     }
 
diff --git a/src/lib/sourceCommit/parseSourceCommit.ts b/src/lib/sourceCommit/parseSourceCommit.ts
index cdd6de4b..b8ba7dac 100644
--- a/src/lib/sourceCommit/parseSourceCommit.ts
+++ b/src/lib/sourceCommit/parseSourceCommit.ts
@@ -25,7 +25,7 @@ export interface Commit {
     labels: string[];
     number: number;
     url: string;
-    mergeCommit: {
+    mergeCommit?: {
       message: string;
       sha: string;
     };
@@ -45,7 +45,7 @@ export interface SourcePullRequestNode {
       name: string;
     }[];
   };
-  mergeCommit: {
+  mergeCommit?: {
     remoteConfigHistory: RemoteConfigHistory['remoteConfigHistory'];
     sha: string;
     message: string;
@@ -171,10 +171,12 @@ export function parseSourceCommit({
           title: sourcePullRequest.title,
           number: sourcePullRequest.number,
           url: sourcePullRequest.url,
-          mergeCommit: {
-            message: sourcePullRequest.mergeCommit.message,
-            sha: sourcePullRequest.mergeCommit.sha,
-          },
+          mergeCommit: sourcePullRequest.mergeCommit
+            ? {
+                message: sourcePullRequest.mergeCommit.message,
+                sha: sourcePullRequest.mergeCommit.sha,
+              }
+            : undefined,
         }
       : undefined,
     sourceBranch: sourcePullRequest?.baseRefName ?? options.sourceBranch,
@@ -278,7 +280,8 @@ function getSourceCommitBranchLabelMapping(
   const sourcePullRequest = getSourcePullRequest(sourceCommit);
 
   const remoteConfig =
-    sourcePullRequest?.mergeCommit.remoteConfigHistory.edges?.[0]?.remoteConfig;
+    sourcePullRequest?.mergeCommit?.remoteConfigHistory.edges?.[0]
+      ?.remoteConfig;
 
   if (remoteConfig) {
     return parseRemoteConfigFile(remoteConfig)?.branchLabelMapping;