diff --git a/git/api/commit.go b/git/api/commit.go
index 76e493797..bf4f96d54 100644
--- a/git/api/commit.go
+++ b/git/api/commit.go
@@ -192,6 +192,9 @@ func (g *Git) listCommitSHAs(
 		if cErr.IsExitCode(128) && cErr.IsAmbiguousArgErr() {
 			return nil, errors.NotFound("reference %q is ambiguous", ref)
 		}
+		if cErr.IsExitCode(128) && cErr.IsBadObject() {
+			return nil, errors.NotFound("commit not found")
+		}
 		return nil, processGitErrorf(err, "failed to trigger rev-list command")
 	}
 
diff --git a/git/api/diff.go b/git/api/diff.go
index 1508bf774..f66339ba0 100644
--- a/git/api/diff.go
+++ b/git/api/diff.go
@@ -156,6 +156,7 @@ func cutLinesFromFullFileDiff(w io.Writer, r io.Reader, startLine, endLine int)
 	return scanner.Err()
 }
 
+//nolint:gocognit
 func (g *Git) RawDiff(
 	ctx context.Context,
 	w io.Writer,
@@ -235,11 +236,14 @@ again:
 			_ = pipeWrite.CloseWithError(err)
 		}()
 
-		if err = newCmd.Run(ctx,
-			command.WithDir(repoPath),
-			command.WithStdout(pipeWrite),
-		); err != nil {
+		err = newCmd.Run(ctx, command.WithDir(repoPath), command.WithStdout(pipeWrite))
+		if err != nil {
 			err = processGitErrorf(err, "git diff failed between %q and %q", baseRef, headRef)
+			if cErr := command.AsError(err); cErr != nil {
+				if cErr.IsExitCode(128) && cErr.IsBadObject() {
+					err = errors.NotFound("commit not found")
+				}
+			}
 		}
 	}()
 
diff --git a/git/command/error.go b/git/command/error.go
index bb424af64..9d32c923d 100644
--- a/git/command/error.go
+++ b/git/command/error.go
@@ -57,6 +57,10 @@ func (e *Error) IsAmbiguousArgErr() bool {
 	return strings.Contains(e.Error(), "ambiguous argument")
 }
 
+func (e *Error) IsBadObject() bool {
+	return strings.Contains(e.Error(), "bad object")
+}
+
 func (e *Error) IsInvalidRefErr() bool {
 	return strings.Contains(e.Error(), "not a valid ref")
 }