diff --git a/core/src/main/java/org/teavm/backend/wasm/render/WasmRenderer.java b/core/src/main/java/org/teavm/backend/wasm/render/WasmRenderer.java
index 3c421a4c7..e30642ec4 100644
--- a/core/src/main/java/org/teavm/backend/wasm/render/WasmRenderer.java
+++ b/core/src/main/java/org/teavm/backend/wasm/render/WasmRenderer.java
@@ -57,14 +57,15 @@ public class WasmRenderer {
         visitor.open().append("module");
         renderTypes(module);
 
+        int functionIndex = 0;
         for (WasmFunction function : module.getFunctions().values()) {
             if (function.getImportName() != null) {
-                lf().render(function);
+                lf().append(";; function #" + functionIndex++).lf().render(function);
             }
         }
         for (WasmFunction function : module.getFunctions().values()) {
             if (function.getImportName() == null) {
-                lf().render(function);
+                lf().append(";; function #" + functionIndex++).lf().render(function);
             }
         }