--- a/libguile/posix-w32.h
+++ b/libguile/posix-w32.h
@@ -75,7 +75,7 @@
 SCM_INTERNAL int waitpid (intptr_t, int *, int);
 SCM_INTERNAL int w32_status_to_termsig (DWORD status);
 
-SCM_INTERNAL int start_child (const char *exec_file, char **argv,
+SCM_INTERNAL pid_t start_child (const char *exec_file, char **argv,
                               int reading, int c2p[2], int writing, int p2c[2],
                               int infd, int outfd, int errfd);