diff --git a/src/apps/altcp_tls/altcp_tls_mbedtls.c b/src/apps/altcp_tls/altcp_tls_mbedtls.c
index 9a4e4aa4..31f9b518 100644
--- a/src/apps/altcp_tls/altcp_tls_mbedtls.c
+++ b/src/apps/altcp_tls/altcp_tls_mbedtls.c
@@ -718,7 +718,7 @@ altcp_mbedtls_debug(void *ctx, int level, const char *file, int line, const char
 #endif
 
 static err_t
-altcp_mbedtls_ref_entropy()
+altcp_mbedtls_ref_entropy(void)
 {
   SYS_ARCH_DECL_PROTECT(old_level);
   SYS_ARCH_PROTECT(old_level);
@@ -742,27 +742,25 @@ altcp_mbedtls_ref_entropy()
         SYS_ARCH_UNPROTECT(old_level);
         return ERR_ARG;
       }
-    }
-    else {
+    } else {
       SYS_ARCH_UNPROTECT(old_level);
       return ERR_MEM;
     }
-  }
-  else
+  } else {
     altcp_tls_entropy_rng->ref++;
+  }
   SYS_ARCH_UNPROTECT(old_level);
   return ERR_OK;
 }
 
-
-
 static void
-altcp_mbedtls_unref_entropy()
+altcp_mbedtls_unref_entropy(void)
 {
   SYS_ARCH_DECL_PROTECT(old_level);
   SYS_ARCH_PROTECT(old_level);
-  if (altcp_tls_entropy_rng && altcp_tls_entropy_rng->ref)
+  if (altcp_tls_entropy_rng && altcp_tls_entropy_rng->ref) {
       altcp_tls_entropy_rng->ref--;
+  }
   SYS_ARCH_UNPROTECT(old_level);
 }