diff --git a/ors-engine/src/main/java/org/heigit/ors/routing/graphhopper/extensions/storages/builders/CsvGraphStorageBuilder.java b/ors-engine/src/main/java/org/heigit/ors/routing/graphhopper/extensions/storages/builders/CsvGraphStorageBuilder.java
index 0b0fc31b53..980c32c413 100644
--- a/ors-engine/src/main/java/org/heigit/ors/routing/graphhopper/extensions/storages/builders/CsvGraphStorageBuilder.java
+++ b/ors-engine/src/main/java/org/heigit/ors/routing/graphhopper/extensions/storages/builders/CsvGraphStorageBuilder.java
@@ -35,6 +35,7 @@ public class CsvGraphStorageBuilder extends AbstractGraphStorageBuilder {
     private CsvGraphStorage storage;
     private final Map<Long, Integer[]> id2Value = new HashMap<>();
     private static final int MAX_VALUE = 100;
+    private static final int MIN_VALUE = -100;
     private final byte defaultValue = 50; // TODO: make configurable
     private String[] columnNames;
 
@@ -105,9 +106,9 @@ private byte[] getValues(long id) {
         } else {
             int index = 0;
             for (Integer i : gi) {
-                if (i > MAX_VALUE) {
-                    throw new AssertionError("Value too large (way id " + id
-                            + " at index " + index + "):" + i + " > " + MAX_VALUE);
+                if (i > MAX_VALUE || i < MIN_VALUE) {
+                    throw new AssertionError("Value out of range (way id " + id
+                            + " at index " + index + "):" + i + " not in [" + MIN_VALUE + "," + MAX_VALUE + "]");
                 }
                 byteValues[index] = i.byteValue();
                 index++;
diff --git a/ors-engine/src/main/java/org/heigit/ors/routing/graphhopper/extensions/weighting/HeatStressWeighting.java b/ors-engine/src/main/java/org/heigit/ors/routing/graphhopper/extensions/weighting/HeatStressWeighting.java
index 880635ab94..71dd19b5db 100644
--- a/ors-engine/src/main/java/org/heigit/ors/routing/graphhopper/extensions/weighting/HeatStressWeighting.java
+++ b/ors-engine/src/main/java/org/heigit/ors/routing/graphhopper/extensions/weighting/HeatStressWeighting.java
@@ -29,10 +29,11 @@ public HeatStressWeighting(FlagEncoder encoder, PMap map, GraphHopperStorage gra
 
     @Override
     public double calcEdgeWeight(EdgeIteratorState edgeState, boolean reverse) {
+        // TODO: this is a short term solution to be adapted when
+        //       AdditionWeighting will be replaced
         if (heatStressStorage != null) {
             int stressLevel = heatStressStorage.getEdgeValue(EdgeIteratorStateHelper.getOriginalEdge(edgeState), columnIndex, buffer);
-            // Convert value range from [0,100] to [1,2] to avoid large detours and multiply by user weighting in API request
-            return (stressLevel * 0.01 * weightingFactor) + 1;
+            return stressLevel * weightingFactor / 100 + 1.0;
         }
 
         return 1.0;