diff --git a/src/fdr/fdr_confirm_compile.cpp b/src/fdr/fdr_confirm_compile.cpp
index d6eb6640..319141c4 100644
--- a/src/fdr/fdr_confirm_compile.cpp
+++ b/src/fdr/fdr_confirm_compile.cpp
@@ -337,6 +337,7 @@ bytecode_ptr<FDRConfirm> getFDRConfirm(const vector<hwlmLiteral> &lits,
     size_t actual_size = ROUNDUP_N((size_t)(ptr - fdrc_base),
                                    alignof(FDRConfirm));
     assert(actual_size <= size);
+    fdrc.shrink(actual_size);
 
     return fdrc;
 }
diff --git a/src/util/bytecode_ptr.h b/src/util/bytecode_ptr.h
index ace5063c..15d3e2fe 100644
--- a/src/util/bytecode_ptr.h
+++ b/src/util/bytecode_ptr.h
@@ -101,6 +101,19 @@ public:
         swap(alignment, other.alignment);
     }
 
+    /**
+     * \brief Reduces the apparent size of the memory region. Note that this
+     * does not reallocate and copy, it just changes the value returned by
+     * size().
+     */
+    void shrink(size_t size) {
+        if (size > bytes) {
+            assert(0);
+            throw std::logic_error("Must shrink to a smaller value");
+        }
+        bytes = size;
+    }
+
     /** \brief Returns size of the memory region in bytes. */
     size_t size() const { return bytes; }