diff --git a/mongoose.c b/mongoose.c
index 7a3ca9e3..9f11ff97 100644
--- a/mongoose.c
+++ b/mongoose.c
@@ -10252,8 +10252,11 @@ char *mg_mprintf(const char *fmt, ...) {
 }
 
 void mg_pfn_stdout(char c, void *param) {
+#if MG_ENABLE_POSIX_FS
   putchar(c);
+#endif
   (void) param;
+  (void) c;
 }
 
 static size_t print_ip4(void (*out)(char, void *), void *arg, uint8_t *p) {
diff --git a/src/printf.c b/src/printf.c
index c6202c7d..1783353d 100644
--- a/src/printf.c
+++ b/src/printf.c
@@ -71,8 +71,11 @@ char *mg_mprintf(const char *fmt, ...) {
 }
 
 void mg_pfn_stdout(char c, void *param) {
+#if MG_ENABLE_POSIX_FS
   putchar(c);
+#endif
   (void) param;
+  (void) c;
 }
 
 static size_t print_ip4(void (*out)(char, void *), void *arg, uint8_t *p) {