--- a/subprojects/frida-gum/gum/backend-linux/gumthreadregistry-linux.c
+++ b/subprojects/frida-gum/gum/backend-linux/gumthreadregistry-linux.c
@@ -11,7 +11,7 @@
 #include "gum/gumlinux.h"
 
 #ifdef HAVE_MUSL
-# define GUM_PTHREAD_FROM_PTR(p) (p)
+# define GUM_PTHREAD_FROM_PTR(p) ((pthread_t) GPOINTER_TO_SIZE (p))
 #else
 # define GUM_PTHREAD_FROM_PTR(p) GPOINTER_TO_SIZE (p)
 #endif