diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8b0587fe2..23293221e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,8 @@
       - replaced lhs/rhs profiles by using test defined profiles
     - Trip Plugin
       - changed internal behaviour to prefer the smallest lexicographic result over the largest one
+    - Bugfixes
+      - fixed a bug where polyline decoding on a defective polyline could end up in out-of-bound access on a vector
 
 # 5.4.0
   - Changes from 5.3.0
diff --git a/src/engine/polyline_compressor.cpp b/src/engine/polyline_compressor.cpp
index 1dc9b7045..11954b5d7 100644
--- a/src/engine/polyline_compressor.cpp
+++ b/src/engine/polyline_compressor.cpp
@@ -100,7 +100,7 @@ std::vector<util::Coordinate> decodePolyline(const std::string &geometry_string)
             b = geometry_string.at(index++) - 63;
             result |= (b & 0x1f) << shift;
             shift += 5;
-        } while (b >= 0x20);
+        } while (b >= 0x20 && index < len);
         int dlat = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1));
         lat += dlat;
 
@@ -111,7 +111,7 @@ std::vector<util::Coordinate> decodePolyline(const std::string &geometry_string)
             b = geometry_string.at(index++) - 63;
             result |= (b & 0x1f) << shift;
             shift += 5;
-        } while (b >= 0x20);
+        } while (b >= 0x20 && index < len);
         int dlng = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1));
         lng += dlng;