diff --git a/src/template-model/src/parser/yaml.rs b/src/template-model/src/parser/yaml.rs
index bae68fa..c04cbac 100644
--- a/src/template-model/src/parser/yaml.rs
+++ b/src/template-model/src/parser/yaml.rs
@@ -257,12 +257,14 @@ impl MarkedEventReceiver for CfnYamlLoader {
                             }
                             self.path_stack.push(v.clone());
                             let path = self.current_path();
-                            // mark.line() and mark.col() are 0-based
-                            self.span_map.insert(path, (mark.line() as u32 + 1, mark.col() as u32 + 1));
+                            // yaml_rust2 Marker reports line 1-based but column 0-based,
+                            // so only the column is shifted to the 1-based column every
+                            // other diagnostic reports (see the parse-error path above).
+                            self.span_map.insert(path, (mark.line() as u32, mark.col() as u32 + 1));
                             // Remember this key's position so a later duplicate of it
                             // can be anchored at the offending occurrence.
                             if let Some(slot) = self.key_marks.last_mut() {
-                                *slot = Some((mark.line() as u32 + 1, mark.col() as u32 + 1));
+                                *slot = Some((mark.line() as u32, mark.col() as u32 + 1));
                             }
                         }
                     } else if matches!(parent.0, Yaml::Array(_))