diff --git a/src/c/stacks.d b/src/c/stacks.d
index 623467307..d22a4f267 100644
--- a/src/c/stacks.d
+++ b/src/c/stacks.d
@@ -279,6 +279,11 @@ ecl_stack_frame_open(cl_env_ptr env, cl_object f, cl_index size)
   return f;
 }
 
+/* clang 19 miscompiles the following function on x86_64. Temporarily
+ * turn off optimizations here. */
+#if defined(__clang__) && __clang_major__ == 19 && defined(__x86_64__)
+[[clang::optnone]]
+#endif
 void
 ecl_stack_frame_push(cl_object f, cl_object o)
 {
@@ -334,6 +339,11 @@ ecl_stack_frame_push_values(cl_object f)
   }
 }
 
+/* clang 19 miscompiles the following function on x86_64. Temporarily
+ * turn off optimizations here. */
+#if defined(__clang__) && __clang_major__ == 19 && defined(__x86_64__)
+[[clang::optnone]]
+#endif
 cl_object
 ecl_stack_frame_pop_values(cl_object f)
 {