diff --git a/modules/lang-expression/src/internalClusterTest/java/org/elasticsearch/script/expression/MoreExpressionIT.java b/modules/lang-expression/src/internalClusterTest/java/org/elasticsearch/script/expression/MoreExpressionIT.java
index 02c17977daf6a..e7d6d127174ec 100644
--- a/modules/lang-expression/src/internalClusterTest/java/org/elasticsearch/script/expression/MoreExpressionIT.java
+++ b/modules/lang-expression/src/internalClusterTest/java/org/elasticsearch/script/expression/MoreExpressionIT.java
@@ -502,7 +502,6 @@ public void testSpecialValueVariable() throws Exception {
         assertThat(stats.getAvg(), equalTo(3.0));
     }
 
-    @AwaitsFix(bugUrl = "https://github.com/elastic/elasticsearch/issues/99156")
     public void testStringSpecialValueVariable() throws Exception {
         // i.e. expression script for term aggregations, which is not allowed
         assertAcked(indicesAdmin().prepareCreate("test").setMapping("text", "type=keyword").get());
diff --git a/modules/lang-expression/src/main/java/org/elasticsearch/script/expression/ExpressionAggregationScript.java b/modules/lang-expression/src/main/java/org/elasticsearch/script/expression/ExpressionAggregationScript.java
index ec9435d9386b5..df08c0908e182 100644
--- a/modules/lang-expression/src/main/java/org/elasticsearch/script/expression/ExpressionAggregationScript.java
+++ b/modules/lang-expression/src/main/java/org/elasticsearch/script/expression/ExpressionAggregationScript.java
@@ -83,7 +83,7 @@ public void setNextAggregationValue(Object value) {
                 // _value isn't used in script if specialValue == null
                 if (specialValue != null) {
                     if (value instanceof Number) {
-                        specialValue.setValue(((Number) value).doubleValue());
+                        specialValue.setValue(leaf, ((Number) value).doubleValue());
                     } else {
                         throw new GeneralScriptException("Cannot use expression with text variable using " + exprScript);
                     }
diff --git a/modules/lang-expression/src/main/java/org/elasticsearch/script/expression/ReplaceableConstDoubleValueSource.java b/modules/lang-expression/src/main/java/org/elasticsearch/script/expression/ReplaceableConstDoubleValueSource.java
index 50a70fccdcd44..903ddaf72340e 100644
--- a/modules/lang-expression/src/main/java/org/elasticsearch/script/expression/ReplaceableConstDoubleValueSource.java
+++ b/modules/lang-expression/src/main/java/org/elasticsearch/script/expression/ReplaceableConstDoubleValueSource.java
@@ -15,20 +15,21 @@
 import org.apache.lucene.search.IndexSearcher;
 
 import java.io.IOException;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
 
 /**
  * A {@link DoubleValuesSource} which has a stub {@link DoubleValues} that holds a dynamically replaceable constant double.
  */
 final class ReplaceableConstDoubleValueSource extends DoubleValuesSource {
-    final ReplaceableConstDoubleValues fv;
 
-    ReplaceableConstDoubleValueSource() {
-        fv = new ReplaceableConstDoubleValues();
-    }
+    private final Map<LeafReaderContext, ReplaceableConstDoubleValues> specialValues = new ConcurrentHashMap<>();
 
     @Override
     public DoubleValues getValues(LeafReaderContext ctx, DoubleValues scores) throws IOException {
-        return fv;
+        ReplaceableConstDoubleValues replaceableConstDoubleValues = new ReplaceableConstDoubleValues();
+        specialValues.put(ctx, replaceableConstDoubleValues);
+        return replaceableConstDoubleValues;
     }
 
     @Override
@@ -38,8 +39,12 @@ public boolean needsScores() {
 
     @Override
     public Explanation explain(LeafReaderContext ctx, int docId, Explanation scoreExplanation) throws IOException {
-        if (fv.advanceExact(docId)) return Explanation.match((float) fv.doubleValue(), "ReplaceableConstDoubleValues");
-        else return Explanation.noMatch("ReplaceableConstDoubleValues");
+        // TODO where is this explain called? I bet it's never tested, and probably never called.
+        ReplaceableConstDoubleValues fv = specialValues.get(ctx);
+        if (fv.advanceExact(docId)) {
+            return Explanation.match((float) fv.doubleValue(), "ReplaceableConstDoubleValues");
+        }
+        return Explanation.noMatch("ReplaceableConstDoubleValues");
     }
 
     @Override
@@ -52,7 +57,9 @@ public int hashCode() {
         return System.identityHashCode(this);
     }
 
-    public void setValue(double v) {
+    public void setValue(LeafReaderContext ctx, double v) {
+        ReplaceableConstDoubleValues fv = specialValues.get(ctx);
+        assert fv != null : "getValues must be called before setValue for any given leaf reader context";
         fv.setValue(v);
     }