diff --git a/CHANGES.txt b/CHANGES.txt
index 69ccf55c5b..29100fc8d9 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -9,6 +9,7 @@
  * Throw BufferOverflowException from DataOutputBuffer for better visibility (CASSANDRA-16214)
  * TLS connections to the storage port on a node without server encryption configured causes java.io.IOException accessing missing keystore (CASSANDRA-16144)
 Merged from 3.11:
+ * SASI's `max_compaction_flush_memory_in_mb` settings over 100GB revert to default of 1GB (CASSANDRA-16071)
 Merged from 3.0:
  * Improved check of num_tokens against the length of initial_token (CASSANDRA-14477)
  * Fix a race condition on ColumnFamilyStore and TableMetrics (CASSANDRA-16228)
diff --git a/NEWS.txt b/NEWS.txt
index 99c8af473f..498fbbbe7d 100644
--- a/NEWS.txt
+++ b/NEWS.txt
@@ -280,6 +280,18 @@ Materialized Views
       to be NOT NULL, and no base primary key columns get automatically included in view definition. You have to
       specify them explicitly now.
 
+3.11.10
+======
+
+Upgrading
+---------
+    - SASI's `max_compaction_flush_memory_in_mb` setting was previously getting interpreted in bytes. From 3.11.8
+      it is correctly interpreted in megabytes, but prior to 3.11.10 previous configurations of this setting will
+      lead to nodes OOM during compaction. From 3.11.10 previous configurations will be detected as incorrect,
+      logged, and the setting reverted to the default value of 1GB. It is up to the user to correct the setting
+      after an upgrade, via dropping and recreating the index. See CASSANDRA-16071 for details.
+
+
 3.11.6
 ======
 
diff --git a/src/java/org/apache/cassandra/index/sasi/conf/IndexMode.java b/src/java/org/apache/cassandra/index/sasi/conf/IndexMode.java
index 93c0101238..93ccc66c25 100644
--- a/src/java/org/apache/cassandra/index/sasi/conf/IndexMode.java
+++ b/src/java/org/apache/cassandra/index/sasi/conf/IndexMode.java
@@ -56,6 +56,7 @@ public class IndexMode
     private static final String INDEX_IS_LITERAL_OPTION = "is_literal";
     private static final String INDEX_MAX_FLUSH_MEMORY_OPTION = "max_compaction_flush_memory_in_mb";
     private static final double INDEX_MAX_FLUSH_DEFAULT_MULTIPLIER = 0.15;
+    private static final long DEFAULT_MAX_MEM_BYTES = (long) (1073741824 * INDEX_MAX_FLUSH_DEFAULT_MULTIPLIER); // 1G default for memtable
 
     public final Mode mode;
     public final boolean isAnalyzed, isLiteral;
@@ -187,9 +188,14 @@ public class IndexMode
         }
 
         long maxMemBytes = indexOptions.get(INDEX_MAX_FLUSH_MEMORY_OPTION) == null
-                ? (long) (1073741824 * INDEX_MAX_FLUSH_DEFAULT_MULTIPLIER) // 1G default for memtable
+                ? DEFAULT_MAX_MEM_BYTES
                 : 1048576L * Long.parseLong(indexOptions.get(INDEX_MAX_FLUSH_MEMORY_OPTION));
 
+        if (maxMemBytes > 100L * 1073741824)
+        {
+            logger.error("{} configured as {} is above 100GB, reverting to default 1GB", INDEX_MAX_FLUSH_MEMORY_OPTION, maxMemBytes);
+            maxMemBytes = DEFAULT_MAX_MEM_BYTES;
+        }
         return new IndexMode(mode, isLiteral, isAnalyzed, analyzerClass, maxMemBytes);
     }