diff --git a/src/codegen/assembler.cc b/src/codegen/assembler.cc
index bf8a0749d2b..7534da8446c 100644
--- a/src/codegen/assembler.cc
+++ b/src/codegen/assembler.cc
@@ -106,7 +106,12 @@ class DefaultAssemblerBuffer : public AssemblerBuffer {
   int size() const override { return static_cast<int>(buffer_.size()); }
 
   std::unique_ptr<AssemblerBuffer> Grow(int new_size) override {
-    DCHECK_LT(size(), new_size);
+    // Guard against signed-int overflow in callers (e.g.
+    // Assembler::GrowBuffer's `int new_size = 2 * old_size`): if the initial
+    // buffer was created above kMaximalBufferSize, the doubled size wraps
+    // negative and silently produces a kMinimalBufferSize (128-byte) buffer,
+    // which the caller then MemMoves ~1 GiB of code into.
+    CHECK_LT(size(), new_size);
     return std::make_unique<DefaultAssemblerBuffer>(new_size);
   }