diff --git a/src/libruntime/target/stm32f4/jerry-assert.c b/src/libruntime/target/stm32f4/jerry-assert.c
index abe859184..88e0a218d 100644
--- a/src/libruntime/target/stm32f4/jerry-assert.c
+++ b/src/libruntime/target/stm32f4/jerry-assert.c
@@ -20,9 +20,9 @@
  * Handle failed assertion
  */
 void __noreturn
-jerry_AssertFail(const char *assertion, /**< assertion condition string */
-                 const char *file, /**< file name */
-                 const uint32_t line) /** line */
+jerry_AssertFail(const char *assertion __unused, /**< assertion condition string */
+                 const char *file __unused, /**< file name */
+                 const uint32_t line __unused) /** line */
 {
   __exit( -ERR_GENERAL);
 } /* jerry_AssertFail */
diff --git a/src/libruntime/target/stm32f4/jerry-libc.c b/src/libruntime/target/stm32f4/jerry-libc.c
index e83e31417..7d0faed61 100644
--- a/src/libruntime/target/stm32f4/jerry-libc.c
+++ b/src/libruntime/target/stm32f4/jerry-libc.c
@@ -36,8 +36,13 @@ __printf(const char *format, /**< format string */
     
     va_start( args, format);
     
-    int ret = vprintf( format, args);
-            
+    /**
+     * TODO: Call internal vprintf implementation when it appears.
+     */
+    int ret = 0;
+
+    JERRY_UNIMPLEMENTED();
+
     va_end( args);
     
     return ret;
@@ -52,7 +57,7 @@ __putchar (int c)
 
 /** exit - cause normal process termination  */
 void __noreturn
-__exit (int status)
+__exit (int status __unused)
 {
   /**
    * TODO: Blink LEDs? status -> binary -> LEDs?