diff --git a/planetiler-core/src/main/java/com/onthegomap/planetiler/geo/DouglasPeuckerSimplifier.java b/planetiler-core/src/main/java/com/onthegomap/planetiler/geo/DouglasPeuckerSimplifier.java
index ac76603a5e..6ccb2bca5e 100644
--- a/planetiler-core/src/main/java/com/onthegomap/planetiler/geo/DouglasPeuckerSimplifier.java
+++ b/planetiler-core/src/main/java/com/onthegomap/planetiler/geo/DouglasPeuckerSimplifier.java
@@ -38,7 +38,7 @@ public class DouglasPeuckerSimplifier {
    * @return the simplified geometry
    */
   public static Geometry simplify(Geometry geom, double distanceTolerance) {
-    if (geom.isEmpty()) {
+    if (geom.isEmpty() || (distanceTolerance < 0.0)) {
       return geom.copy();
     }
 
diff --git a/planetiler-core/src/test/java/com/onthegomap/planetiler/FeatureMergeTest.java b/planetiler-core/src/test/java/com/onthegomap/planetiler/FeatureMergeTest.java
index 4a3a38ca16..5a1b713ac0 100644
--- a/planetiler-core/src/test/java/com/onthegomap/planetiler/FeatureMergeTest.java
+++ b/planetiler-core/src/test/java/com/onthegomap/planetiler/FeatureMergeTest.java
@@ -165,6 +165,21 @@ void simplifyLineStringIfToleranceIsSet() {
         true
       )
     );
+    // but doesn't resimplify if the tolerance is negative even when resimplify=true
+    assertEquals(
+      List.of(
+        feature(1, newLineString(10, 10, 20, 20, 30, 30), Map.of("a", 1))
+      ),
+      FeatureMerge.mergeLineStrings(
+        List.of(
+          feature(1, newLineString(10, 10, 20, 20, 30, 30), Map.of("a", 1))
+        ),
+        0,
+        -1,
+        0,
+        true
+      )
+    );
   }
 
   @Test