diff --git a/src/io/plot_style.rs b/src/io/plot_style.rs
index becceca44..89b2033c6 100644
--- a/src/io/plot_style.rs
+++ b/src/io/plot_style.rs
@@ -357,13 +357,8 @@ impl PlotStyleTable {
         let description = self.description.replace(['\r', '\n'], " ");
         s.push_str(&format!("description=\"{description}\n"));
         s.push_str("aci_table_available=TRUE\n");
-        // The factor scales every lineweight when applied, so write it in full,
-        // keeping the decimal point on a whole value.
-        let mut scale_factor = self.scale_factor.to_string();
-        if scale_factor.chars().all(|c| c.is_ascii_digit() || c == '-') {
-            scale_factor.push_str(".0");
-        }
-        s.push_str(&format!("scale_factor={scale_factor}\n"));
+        // The factor scales every lineweight when applied, so write it in full.
+        s.push_str(&format!("scale_factor={}\n", full_real(self.scale_factor)));
         s.push_str(&format!(
             "apply_factor={}\n",
             if self.apply_factor { "TRUE" } else { "FALSE" }
@@ -420,7 +415,7 @@ impl PlotStyleTable {
         }
         s.push_str("}\ncustom_lineweight_table{\n");
         for (index, weight) in self.lineweights.iter().enumerate() {
-            s.push_str(&format!(" {index}={weight:.2}\n"));
+            s.push_str(&format!(" {index}={}\n", full_real(*weight)));
         }
         s.push_str("}\n");
         s
@@ -512,6 +507,15 @@ fn adler32(bytes: &[u8]) -> u32 {
     (b << 16) | a
 }
 
+/// A real number written in full, keeping the decimal point on a whole value.
+fn full_real(value: f32) -> String {
+    let mut text = value.to_string();
+    if text.chars().all(|c| c.is_ascii_digit() || c == '-') {
+        text.push_str(".0");
+    }
+    text
+}
+
 fn packed_rgb([r, g, b]: [u8; 3]) -> i32 {
     u32::from_be_bytes([0xC2, r, g, b]) as i32
 }
@@ -780,4 +784,16 @@ mod round_trip_tests {
         assert!(table.to_text().contains("\nscale_factor=1.0\n"));
         assert_eq!(saved_and_reloaded(&table).scale_factor, 1.0);
     }
+
+    /// Saving keeps each custom lineweight as the table holds it. They used to
+    /// be cut to two decimals, so a 0.035 mm pen came back as a 0.04 mm one.
+    #[test]
+    fn custom_lineweights_survive_a_save() {
+        let mut table = PlotStyleTable::identity("pens.ctb");
+        table.lineweights[1] = 0.035;
+        table.aci_entries[1].lineweight = 1;
+        let reloaded = saved_and_reloaded(&table);
+        assert_eq!(reloaded.lineweights, table.lineweights);
+        assert_eq!(reloaded.resolve_lineweight(1), Some(0.035));
+    }
 }