diff --git a/src/hb-wasm-api.h b/src/hb-wasm-api.h
index 7f25b996a..5af0ecd6b 100644
--- a/src/hb-wasm-api.h
+++ b/src/hb-wasm-api.h
@@ -69,7 +69,7 @@ HB_WASM_BEGIN_DECLS
 #define ref_t uint32_t
 #endif
 #ifndef ptr_t
-#define ptr_t uint32_t
+#define ptr_t(type_t) type_t *
 #endif
 
 typedef uint32_t tag_t;
@@ -79,8 +79,9 @@ typedef ref_t face_t;
 typedef ref_t font_t;
 typedef ref_t buffer_t;
 
-typedef struct {
-  ref_t data;
+typedef struct
+{
+  ptr_t(char) data;
   uint32_t length;
 } blob_t;
 
diff --git a/src/hb-wasm-api.hh b/src/hb-wasm-api.hh
index b245222f7..a005024c9 100644
--- a/src/hb-wasm-api.hh
+++ b/src/hb-wasm-api.hh
@@ -36,7 +36,9 @@
 #define HB_WASM_API_COMPOUND(ret_t, name) HB_INTERNAL void name
 
 #define HB_WASM_EXEC_ENV wasm_exec_env_t exec_env,
-#define HB_WASM_EXEC_ENV_COMPOUND wasm_exec_env_t exec_env, ptr_t retptr,
+#define HB_WASM_EXEC_ENV_COMPOUND wasm_exec_env_t exec_env, ptr_t() retptr,
+
+#define ptr_t(type_t) uint32_t
 
 #include "hb-wasm-api.h"