diff --git a/Makefile b/Makefile
index 1de7fbc..4226aa3 100644
--- a/Makefile
+++ b/Makefile
@@ -1,7 +1,11 @@
-CC=clang
+CC ?= clang
+CFLAGS ?=
 
 all:
-	$(CC) -o lbr -O2 -Wall -Wextra -Wpedantic src/*.c
+	$(CC) -o lbr -O2 -Wall -Wextra -Wpedantic $(CFLAGS) src/*.c
+
+clean:
+	rm lbr
 
 test:
-	./lbr tests/test.lb
\ No newline at end of file
+	./lbr tests/test.lb
diff --git a/src/execute.c b/src/execute.c
index 8b0b84d..d86a16d 100644
--- a/src/execute.c
+++ b/src/execute.c
@@ -532,11 +532,7 @@ void execute(Stack *stack, Stack *originstack, char *modname)
 
         if (!strcmp(NAME, "size"))
         {
-            int i = 0;
-            while (i < stack->pointer)
-                i++;
-
-            stack_push(stack, i);
+            stack_push(stack, stack->pointer);
             continue;
         }
 
diff --git a/tests/native_test.c b/tests/native_test.c
new file mode 100644
index 0000000..d8126e4
--- /dev/null
+++ b/tests/native_test.c
@@ -0,0 +1,14 @@
+#include <stdlib.h>
+#include <stdio.h>
+
+// Build with
+// cc -shared -fPIC native_test.c -o native_test.so
+// or
+// cc -shared -fPIC native_test.c -o native_test.dll
+
+int labashka(unsigned short (*pop)(void), void (*push)(unsigned short), size_t (*len)(void), size_t max_size ) {
+    printf("At %zu, there's %d.\n", len(), pop());
+    push(12);
+    printf("Maximum size is %zu.\n", max_size);
+    return 0;   
+}
diff --git a/tests/native_test.lb b/tests/native_test.lb
new file mode 100644
index 0000000..2a42825
--- /dev/null
+++ b/tests/native_test.lb
@@ -0,0 +1,3 @@
+@ 0
+ push -1
+ #native native_test