diff --git a/apkdmverity/src/main.rs b/apkdmverity/src/main.rs
index 54d5def..321f79a 100644
--- a/apkdmverity/src/main.rs
+++ b/apkdmverity/src/main.rs
@@ -98,7 +98,9 @@
     // Parse the idsig file to locate the merkle tree in it, then attach the file to a loop device
     // with the offset so that the start of the merkle tree becomes the beginning of the loop
     // device.
-    let sig = V4Signature::from(File::open(&idsig)?)?;
+    let sig = V4Signature::from(
+        File::open(&idsig).context(format!("Failed to open idsig file {:?}", &idsig))?,
+    )?;
     let offset = sig.merkle_tree_offset;
     let size = sig.merkle_tree_size as u64;
     let hash_device = loopdevice::attach(&idsig, offset, size)?;