diff --git a/src/mutate.rs b/src/mutate.rs
index bf7ebdd1..52f371dd 100644
--- a/src/mutate.rs
+++ b/src/mutate.rs
@@ -191,11 +191,14 @@ impl Mutant {
             .with_context(|| format!("failed to write mutated code to {path:?}"))
     }
 
+    /// Return a string describing this mutant that's suitable for building a log file name,
+    /// but can contain slashes.
     pub fn log_file_name_base(&self) -> String {
         format!(
-            "{}_line_{}",
-            self.source_file.tree_relative_slashes(),
-            self.span.start.line,
+            "{filename}_line_{line}_col_{col}",
+            filename = self.source_file.tree_relative_slashes(),
+            line = self.span.start.line,
+            col = self.span.start.column,
         )
     }
 }
diff --git a/tests/cli/main.rs b/tests/cli/main.rs
index 4c936f2a..df584ee2 100644
--- a/tests/cli/main.rs
+++ b/tests/cli/main.rs
@@ -506,7 +506,7 @@ fn small_well_tested_tree_is_clean() {
     let log_content = fs::read_to_string(
         tmp_src_dir
             .path()
-            .join("mutants.out/log/src__lib.rs_line_5.log"),
+            .join("mutants.out/log/src__lib.rs_line_5_col_5.log"),
     )
     .unwrap()
     .replace('\r', "");
diff --git a/tests/cli/snapshots/cli__factorial__log_names.snap b/tests/cli/snapshots/cli__factorial__log_names.snap
index a608a2c5..fff4f17b 100644
--- a/tests/cli/snapshots/cli__factorial__log_names.snap
+++ b/tests/cli/snapshots/cli__factorial__log_names.snap
@@ -4,7 +4,7 @@ expression: "&names"
 ---
 [
     "baseline.log",
-    "src__bin__factorial.rs_line_2.log",
-    "src__bin__factorial.rs_line_8.log",
-    "src__bin__factorial.rs_line_8_001.log",
+    "src__bin__factorial.rs_line_2_col_5.log",
+    "src__bin__factorial.rs_line_8_col_5.log",
+    "src__bin__factorial.rs_line_8_col_5_001.log",
 ]