diff --git a/common/command.cc b/common/command.cc
index 56327847..2167deb9 100644
--- a/common/command.cc
+++ b/common/command.cc
@@ -174,7 +174,9 @@ po::options_description CommandHandler::getGeneralOptions()
                           "placer heap criticality exponent (int, default: 2)");
     general.add_options()("placer-heap-timingweight", po::value<int>(), "placer heap timing weight (int, default: 10)");
 
+#if !defined(__wasm)
     general.add_options()("parallel-refine", "use new experimental parallelised engine for placement refinement");
+#endif
 
     general.add_options()("router2-heatmap", po::value<std::string>(),
                           "prefix for router2 resource congestion heatmaps");
diff --git a/common/parallel_refine.cc b/common/parallel_refine.cc
index ea97b852..c2905480 100644
--- a/common/parallel_refine.cc
+++ b/common/parallel_refine.cc
@@ -18,8 +18,11 @@
  */
 
 #include "parallel_refine.h"
-#include "fast_bels.h"
 #include "log.h"
+
+#if !defined(__wasm)
+
+#include "fast_bels.h"
 #include "timing.h"
 #include "scope_lock.h"
 
@@ -944,3 +947,16 @@ bool parallel_refine(Context *ctx, ParallelRefineCfg cfg)
 }
 
 NEXTPNR_NAMESPACE_END
+
+#else /* !defined(__wasm) */
+
+NEXTPNR_NAMESPACE_BEGIN
+
+bool parallel_refine(Context *ctx, ParallelRefineCfg cfg)
+{
+    log_abort();
+}
+
+NEXTPNR_NAMESPACE_END
+
+#endif