diff --git a/zingo-cli/Cargo.toml b/zingo-cli/Cargo.toml
index b881b1f9c..4479bb604 100644
--- a/zingo-cli/Cargo.toml
+++ b/zingo-cli/Cargo.toml
@@ -26,3 +26,6 @@ shellwords = { workspace = true }
 tokio = { workspace = true }
 tracing-subscriber = { workspace = true }
 zip32 = { workspace = true }
+
+[dev-dependencies]
+tempfile = "3"
diff --git a/zingo-cli/src/lib.rs b/zingo-cli/src/lib.rs
index 1f7efeffd..df1ed133c 100644
--- a/zingo-cli/src/lib.rs
+++ b/zingo-cli/src/lib.rs
@@ -398,7 +398,16 @@ If you don't remember the block height, you can pass '--birthday 0' to scan from
         };
 
         let data_dir = if let Some(dir) = matches.get_one::<String>("data-dir") {
-            PathBuf::from(dir.clone())
+            let path = PathBuf::from(dir.clone());
+            if path.is_file() {
+                return Err(format!(
+                    "--data-dir must be a directory, not a file.\n\
+                     You provided: {dir}\n\
+                     Hint: use the parent directory instead, e.g. --data-dir {}",
+                    path.parent().map(|p| p.display().to_string()).unwrap_or_else(|| ".".into())
+                ));
+            }
+            path
         } else {
             PathBuf::from("wallets")
         };
diff --git a/zingo-cli/src/tests.rs b/zingo-cli/src/tests.rs
index 5c3b91b61..c9a5531ec 100644
--- a/zingo-cli/src/tests.rs
+++ b/zingo-cli/src/tests.rs
@@ -500,6 +500,14 @@ mod config_template {
             let err = fill(&[examples::BIN_NAME, "--server", "https://example.com"]).unwrap_err();
             assert!(err.contains("scheme"));
         }
+
+        #[test]
+        fn data_dir_is_a_file() {
+            let tmp = tempfile::NamedTempFile::new().unwrap();
+            let file_path = tmp.path().to_str().unwrap();
+            let err = fill(&[examples::BIN_NAME, "--data-dir", file_path]).unwrap_err();
+            assert!(err.contains("must be a directory, not a file"));
+        }
     }
 
     mod zingo_config {