diff --git a/docs/TODO.txt b/docs/TODO.txt
index 3bc560e..428861d 100644
--- a/docs/TODO.txt
+++ b/docs/TODO.txt
@@ -19,13 +19,12 @@ DONE: functions are invoked by calling their names
 DONE: function arguments can have specified types
 DONE: function returns can have specified types
 DONE: closures are explicitly supported
+DONE: functions are first-class citizens
+DONE: functions take a set number of parameters
 
 
-TODO: functions take a set number of parameters
-TODO: functions can return a set number of values
-TODO: functions are first-class citizens
+TODO: functions return a set number of values
 TODO: functions last argument can be a rest parameter
-TODO: check for wrong number of function parameters
 
 TODO: Nullish types
 TODO: A way to check the type of a variable (typeOf keyword)
diff --git a/docs/spec.md b/docs/spec.md
index 798cd4f..3f39eec 100644
--- a/docs/spec.md
+++ b/docs/spec.md
@@ -275,7 +275,7 @@ fn doSomething() {
 }
 ```
 
-Functions can take a number of parameters within the parenthesis following their names, and can return a number of values to the calling context using the return keyword.
+Functions can take a set number of parameters within the parenthesis following their names, and can return a number of values to the calling context using the return keyword.
 
 ```
 fn reverseOrder(a, b, c) { //return type isn't required by default
diff --git a/scripts/function.toy b/scripts/function.toy
deleted file mode 100644
index ef50ac4..0000000
--- a/scripts/function.toy
+++ /dev/null
@@ -1,51 +0,0 @@
-/*
-fn name(param1: string, param2: string, param3): string {
-	print "foobar";
-	print param1;
-	return param2;
-}
-
-var result = name("hello world", "goodnight world");
-
-print "fizz";
-print result;
-print "buzz";
-
-
-*/
-
-/*
-fn outer() {
-	fn inner() {
-		print "foo";
-	}
-
-	inner();
-
-	return inner;
-}
-
-var handle = outer();
-
-handle(); //breaks
-*/
-
-
-fn make() {
-	var counter = 0;
-
-	fn count() {
-		return counter++;
-	}
-
-	return count;
-}
-
-var tally = make();
-
-print tally();
-print tally();
-print tally();
-print tally();
-print tally();
-
diff --git a/source/compiler.c b/source/compiler.c
index 5631832..dd5bbb7 100644
--- a/source/compiler.c
+++ b/source/compiler.c
@@ -426,6 +426,25 @@ static void writeCompilerWithJumps(Compiler* compiler, Node* node, void* breakAd
 				}
 			}
 
+			//push the argument COUNT to the top of the stack
+			int argumentsCount = findLiteralIndex(&compiler->literalCache, TO_INTEGER_LITERAL(node->fnCall.arguments->fnCollection.count));
+			if (argumentsCount < 0) {
+				argumentsCount = pushLiteralArray(&compiler->literalCache, TO_INTEGER_LITERAL(node->fnCall.arguments->fnCollection.count));
+			}
+
+			if (argumentsCount >= 256) {
+				//push a "long" index
+				compiler->bytecode[compiler->count++] = OP_LITERAL_LONG; //1 byte
+
+				*((unsigned short*)(compiler->bytecode + compiler->count)) = (unsigned short)argumentsCount; //2 bytes
+				compiler->count += sizeof(unsigned short);
+			}
+			else {
+				//push the index
+				compiler->bytecode[compiler->count++] = OP_LITERAL; //1 byte
+				compiler->bytecode[compiler->count++] = (unsigned char)argumentsCount; //1 byte
+			}
+
 			//call the function
 			//DO NOT call the collection, this is done in binary
 		}
diff --git a/source/interpreter.c b/source/interpreter.c
index c361227..c39c16a 100644
--- a/source/interpreter.c
+++ b/source/interpreter.c
@@ -750,8 +750,10 @@ static bool execFnCall(Interpreter* interpreter) {
 	LiteralArray arguments;
 	initLiteralArray(&arguments);
 
-	//unpack the arguments
-	while (interpreter->stack.count > 1) {
+	Literal stackSize = popLiteralArray(&interpreter->stack);
+
+	//unpack the stack of arguments
+	for (int i = 0; i < AS_INTEGER(stackSize); i++) {
 		pushLiteralArray(&arguments, popLiteralArray(&interpreter->stack)); //NOTE: also reverses the order
 	}
 
@@ -780,6 +782,19 @@ static bool execFnCall(Interpreter* interpreter) {
 	LiteralArray* paramArray = AS_ARRAY(inner.literalCache.literals[ readShort(inner.bytecode, &inner.count) ]);
 	LiteralArray* returnArray = AS_ARRAY(inner.literalCache.literals[ readShort(inner.bytecode, &inner.count) ]);
 
+	//check the param total is correct
+	if (paramArray->count != arguments.count * 2) {
+		printf(ERROR "ERROR: Incorrect number of arguments passed to function \"\n");
+		printLiteral(identifier);
+		printf("\"\n" RESET);
+
+		//free, and skip out
+		freeLiteralArray(&arguments);
+		freeInterpreter(&inner);
+
+		return false;
+	}
+
 	for (int i = 0; i < paramArray->count; i += 2) { //contents is the indexes of identifier & type
 		//declare and define each entry in the scope
 		if (!declareScopeVariable(inner.scope, paramArray->literals[i], paramArray->literals[i + 1])) {
diff --git a/test/functions.toy b/test/functions.toy
new file mode 100644
index 0000000..24be460
--- /dev/null
+++ b/test/functions.toy
@@ -0,0 +1,32 @@
+//test function return
+fn testFourtyTwo() {
+	return 42;
+}
+
+assert testFourtyTwo() == 42, "function returns failed";
+
+
+//test function parameters
+fn identity(x) {
+	return x;
+}
+
+assert identity("hello world") == "hello world", "identity function failed";
+
+
+//test closures
+fn make() {
+	var counter = 0;
+
+	fn count() {
+		return ++counter;
+	}
+
+	return count;
+}
+
+var tally = make();
+
+assert tally() == 1 && tally() == 2, "Closures failed";
+
+print "All good";
\ No newline at end of file