diff --git a/README.md b/README.md
index 8b336ad..da728bb 100644
--- a/README.md
+++ b/README.md
@@ -75,19 +75,19 @@ let @main in {
 ## Examples that actually work right now
 Exit with exit code 0 (success):
 ```
-let @main in {
+let @main : i32 in {
 	0
 }
 ```
 Exit with non-zero exit code (failure):
 ```
-let @main in {
+let @main : i32 in {
 	1 // or any other number
 }
 ```
 Exit with calculated exit code (yes, this language is a glorified calculator right now):
 ```
-let @main in {
+let @main : i32 in {
 	3 + 5 * 6 // It doesn't even support parentheses, what a failure
 } // the exit code is actually computed at compile time by LLVM (optimizations!!)
 ```
diff --git a/src/Parser.cpp b/src/Parser.cpp
index 9e2ca94..ed3fcdc 100644
--- a/src/Parser.cpp
+++ b/src/Parser.cpp
@@ -8,6 +8,9 @@
 
 Parser::Parser(const TokenStream& tokens) : tokens(tokens)
 {
+    m_type_map = {{"void", llvm::Type::getVoidTy(*globalContext)}, {"bool", llvm::Type::getInt1Ty(*globalContext)},
+                  {"i8", llvm::Type::getInt8Ty(*globalContext)},   {"i16", llvm::Type::getInt16Ty(*globalContext)},
+                  {"i32", llvm::Type::getInt32Ty(*globalContext)}, {"i64", llvm::Type::getInt64Ty(*globalContext)}};
 }
 
 std::shared_ptr<Parser> Parser::new_parser(const TokenStream& tokens)
@@ -101,8 +104,8 @@ Result<TopLevelNode> Parser::function()
 {
     FunctionPrototype proto;
     Token* start_token = current_token;
-    proto.returnType = llvm::IntegerType::getInt32Ty(*globalContext); // FIXME: allow specifying return type
-    proto.arguments = {};                                             // FIXME: allow specifying arguments
+    proto.returnType = m_type_map["void"]; // FIXME: allow specifying return type
+    proto.arguments = {};                  // FIXME: allow specifying arguments
     if (current_token->type != TT_Let) return Err<TopLevelNode>("Expected let", current_token);
     advance();
     if (current_token->type != TT_At) return Err<TopLevelNode>("Expected @", current_token);
@@ -114,13 +117,37 @@ Result<TopLevelNode> Parser::function()
         proto.name = current_token->string_value.value();
     }
     advance();
-    if (current_token->type != TT_In && current_token->type != TT_Semicolon)
-        return Err<TopLevelNode>("Expected 'in' or semicolon", current_token);
+    if (current_token->type != TT_In && current_token->type != TT_Semicolon && current_token->type != TT_Colon)
+        return Err<TopLevelNode>("Expected 'in', colon or semicolon", current_token);
     if (current_token->type == TT_Semicolon)
     {
         advance();
         return Ok<TopLevelNode>(new EmptyFunctionNode(proto), start_token);
     }
+    if (current_token->type == TT_Colon)
+    {
+        advance();
+        if (current_token->type != TT_Identifier)
+        {
+            return Err<TopLevelNode>("Expected type name", current_token);
+        }
+        try
+        {
+            proto.returnType = m_type_map.at(current_token->string_value.value());
+        }
+        catch (std::out_of_range)
+        {
+            return Err<TopLevelNode>("Expected type name", current_token);
+        }
+        advance();
+        if (current_token->type != TT_In && current_token->type != TT_Semicolon)
+            return Err<TopLevelNode>("Expected 'in' or semicolon", current_token);
+        if (current_token->type == TT_Semicolon)
+        {
+            advance();
+            return Ok<TopLevelNode>(new EmptyFunctionNode(proto), start_token);
+        }
+    }
     advance();
     if (current_token->type != TT_LBracket)
         return Err<TopLevelNode>("Invalid syntax",
diff --git a/src/Parser.h b/src/Parser.h
index 12ca99b..5b8acd2 100644
--- a/src/Parser.h
+++ b/src/Parser.h
@@ -6,6 +6,7 @@
 #include "Lexer.h"
 #include "Result.h"
 #include "sapphirepch.h"
+#include "llvm/IR/Type.h"
 
 /* Parser class for the Sapphire compiler. */
 class Parser
@@ -17,6 +18,8 @@ class Parser
     int advance();
     Token* current_token;
 
+    std::unordered_map<std::string, llvm::Type*> m_type_map;
+
     Result<ExprNode> factor();
     Result<ExprNode> expr();
     Result<ExprNode> term();
diff --git a/tests/calc.sp b/tests/calc.sp
index 5656a54..5980bbd 100644
--- a/tests/calc.sp
+++ b/tests/calc.sp
@@ -1,3 +1,3 @@
-let @main in {
+let @main : i32 in {
     1 + 3 * 5
 }
\ No newline at end of file
diff --git a/tests/wimport.json b/tests/wimport.json
index e038d90..dfb4e6e 100644
--- a/tests/wimport.json
+++ b/tests/wimport.json
@@ -1,9 +1,7 @@
 {
     "file": "wimport.sp",
     "compile": {
-        "flags": [
-            "--wimport"
-        ],
+        "flags": [],
         "exit-code": 1,
         "stdout": "",
         "stderr": "\u001b[1;1mtests/wimport.sp:1:1: \u001b[31;49merror: \u001b[0;0mExpected let\n1    \n     \u001b[31;49m^\u001b[0;0m\n"