diff --git a/Makefile b/Makefile
index a539baa..e2d9d4b 100644
--- a/Makefile
+++ b/Makefile
@@ -25,10 +25,12 @@ VPATH           := $(SRC_DIR) $(wildcard $(LIB_DIR)/*)
 
 .DEFAULT_GOAL   := all
 
-.PHONY: all clean cleanall
+.PHONY: all multi clean cleanall
 
+all:
+	@$(MAKE) -s -j multi
 
-all: $(BUILD_DIR)/server $(BUILD_DIR)/client
+multi: $(BUILD_DIR)/server $(BUILD_DIR)/client
 	@echo "Compiled!"
 
 
diff --git a/lib/api/api.c b/lib/api/api.c
index 812ec5d..4fd5f0e 100644
--- a/lib/api/api.c
+++ b/lib/api/api.c
@@ -197,7 +197,7 @@ int openFile(const char* pathname, int flags) {
 	return -1;
     }
     if(isOpen(pathname, flags)) { // already open
-	return 0;
+	return -1;
     }
 
     // invio al server la stringa "openFile|$(pathname)|$(flags)"