diff --git a/src/ccutil/indexmapbidi.cpp b/src/ccutil/indexmapbidi.cpp
index df95a97874..e97ef49d56 100644
--- a/src/ccutil/indexmapbidi.cpp
+++ b/src/ccutil/indexmapbidi.cpp
@@ -21,6 +21,11 @@
 
 namespace tesseract {
 
+// Destructor.
+// It is defined here, so the compiler can create a single vtable
+// instead of weak vtables in every compilation unit.
+IndexMap::~IndexMap() = default;
+
 // SparseToCompact takes a sparse index to an index in the compact space.
 // Uses a binary search to find the result. For faster speed use
 // IndexMapBiDi, but that takes more memory.
diff --git a/src/ccutil/indexmapbidi.h b/src/ccutil/indexmapbidi.h
index 9a773729c7..6d62fd4a27 100644
--- a/src/ccutil/indexmapbidi.h
+++ b/src/ccutil/indexmapbidi.h
@@ -41,7 +41,7 @@ class IndexMapBiDi;
 // It must be initialized by copying from an IndexMapBiDi or by DeSerialize.
 class IndexMap {
  public:
-  virtual ~IndexMap() = default;
+  virtual ~IndexMap();
 
   // SparseToCompact takes a sparse index to an index in the compact space.
   // Uses a binary search to find the result. For faster speed use