diff --git a/code/libraries/btree/src/main/java/nu/marginalia/btree/BTreeReader.java b/code/libraries/btree/src/main/java/nu/marginalia/btree/BTreeReader.java
index cec925e6..778e921a 100644
--- a/code/libraries/btree/src/main/java/nu/marginalia/btree/BTreeReader.java
+++ b/code/libraries/btree/src/main/java/nu/marginalia/btree/BTreeReader.java
@@ -123,9 +123,7 @@ public class BTreeReader {
      */
     public long[] queryData(long[] keys, int offset) {
 
-        if (getClass().desiredAssertionStatus()) {
-            assert(isSorted(keys));
-        }
+        assert(isSorted(keys)) : "The input array docIds is assumed to be sorted";
 
         if (header.layers() == 0) {
             return queryDataNoIndex(keys, offset);
diff --git a/code/libraries/btree/src/main/java/nu/marginalia/btree/BTreeWriter.java b/code/libraries/btree/src/main/java/nu/marginalia/btree/BTreeWriter.java
index a359edcd..13aca70a 100644
--- a/code/libraries/btree/src/main/java/nu/marginalia/btree/BTreeWriter.java
+++ b/code/libraries/btree/src/main/java/nu/marginalia/btree/BTreeWriter.java
@@ -41,6 +41,8 @@ public class BTreeWriter {
             throw new IllegalStateException("Dog ear was not overwritten: " + header);
         }
 
+        assert slice.isSortedN(ctx.entrySize) : "Provided data was not sorted";
+
         if (header.layers() >= 1) { // Omit layer if data fits within a single block
             writeIndex(header);
         }