diff --git a/clib/json11.cpp b/clib/json11.cpp
index 4ef6e8b..7ca7c42 100644
--- a/clib/json11.cpp
+++ b/clib/json11.cpp
@@ -137,11 +137,11 @@ namespace json11 {
     }
 
     static MlValue ivalualize(int value) {
-	    return MlValue(value);
+	    return MlValue((long)value);
     }
 
     static MlValue ivalualize(bool value) {
-	    return MlValue(value);
+	    return MlValue((long)value);
     }
 
     static MlValue ivalualize(const string &value) {
diff --git a/ml.cpp b/ml.cpp
index b7982c0..6a618c2 100644
--- a/ml.cpp
+++ b/ml.cpp
@@ -61,7 +61,7 @@ bool is_symbol(char ch) {
 
 MlValue::MlValue() : type(NIL) {}
 
-MlValue::MlValue(int i) : type(INT) { stack_data.i = i; }
+MlValue::MlValue(long i) : type(INT) { stack_data.i = i; }
 
 MlValue::MlValue(double f) : type(FLOAT) { stack_data.f = f; }
 
@@ -168,11 +168,11 @@ bool MlValue::is_number() const {
 
 // Get the "truthy" boolean value of this value.
 bool MlValue::as_bool() const {
-	return type != NIL && *this != MlValue(0);	// TODO remove 0 as false
+	return type != NIL && *this != MlValue(0l);	// TODO remove 0 as false
 }
 
 // Get this item's integer value
-int MlValue::as_int() const {
+long MlValue::as_int() const {
 	return cast_to_int().stack_data.i;
 }
 
@@ -237,7 +237,7 @@ MlValue MlValue::cast_to_int() const {
 		case INT:
 			return *this;
 		case FLOAT:
-			return MlValue(int(stack_data.f));
+			return MlValue(long(stack_data.f));
 			// Only ints and floats can be cast to an int
 		default:
 			throw MlError(*this, MlEnvironment(), BAD_CAST);
@@ -778,8 +778,8 @@ MlValue parse(std::string &s, int &ptr) {
 		skip_whitespace(s, ptr);
 
 		if (n.find('.') != std::string::npos)
-			return MlValue((negate ? -1 : 1) * atof(n.c_str()));
-		else return MlValue((negate ? -1 : 1) * atoi(n.c_str()));
+			return MlValue((negate ? -1l : 1l) * atof(n.c_str()));
+		else return MlValue((negate ? -1l : 1l) * atol(n.c_str()));
 
 	} else if (s[ptr] == '\"') {
 		// If this is a string
@@ -903,7 +903,7 @@ namespace builtin {
 	    else if (args.size() == 3)
 			return args[2].eval(env);
 
-		return MlValue(0);
+		return MlValue(0l);
     }
 
     // Define a variable with a value (SPECIAL FORM)
@@ -1031,7 +1031,7 @@ namespace builtin {
 	    if (args.size() != 2)
 		    throw MlError(MlValue("random", random), env, args.size() > 2 ? TOO_MANY_ARGS : TOO_FEW_ARGS);
 
-	    int low = args[0].as_int(), high = args[1].as_int();
+	    long low = args[0].as_int(), high = args[1].as_int();
 	    return MlValue(rand() % (high - low + 1) + low);
     }
 
@@ -1064,7 +1064,7 @@ namespace builtin {
 	    if (args.size() != 2)
 		    throw MlError(MlValue("write-file", write_file), env, args.size() > 2 ? TOO_MANY_ARGS : TOO_FEW_ARGS);
 
-	    return MlValue(write_file_contents(args[0].as_string(), args[1].as_string()));
+	    return MlValue((long)write_file_contents(args[0].as_string(), args[1].as_string()));
     }
 
     // Read URL to (code content)
@@ -1086,7 +1086,7 @@ namespace builtin {
 		    }
 	    }
 
-	    std::pair<int, std::string> result = client.doGetRequest(args[0].as_string(), headers);
+	    std::pair<long, std::string> result = client.doGetRequest(args[0].as_string(), headers);
 	    // TODO add helper function for this
 	    std::vector<MlValue> lst;
 	    lst.push_back(MlValue(result.first));
@@ -1187,7 +1187,7 @@ namespace builtin {
 	    if (args.size() != 1)
 		    throw MlError(MlValue("is-file?", is_file), env, args.size() > 1 ? TOO_MANY_ARGS : TOO_FEW_ARGS);
 
-	    return MlValue(is_path_file(args[0].as_string()));
+	    return MlValue((long)is_path_file(args[0].as_string()));
     }
 
     // is_path directory
@@ -1198,7 +1198,7 @@ namespace builtin {
 	    if (args.size() != 1)
 		    throw MlError(MlValue("is-dir?", is_dir), env, args.size() > 1 ? TOO_MANY_ARGS : TOO_FEW_ARGS);
 
-	    return MlValue(is_path_dir(args[0].as_string()));
+	    return MlValue((long)is_path_dir(args[0].as_string()));
     }
 
     // Read a file and execute its code
@@ -1292,7 +1292,7 @@ namespace builtin {
 
 	    if (args.size() != 2)
 		    throw MlError(MlValue("=", eq), env, args.size() > 2 ? TOO_MANY_ARGS : TOO_FEW_ARGS);
-	    return MlValue(int(args[0] == args[1]));
+	    return MlValue(long(args[0] == args[1]));
     }
 
     // Are two values not equal?
@@ -1301,7 +1301,7 @@ namespace builtin {
 
 	    if (args.size() != 2)
 		    throw MlError(MlValue("!=", neq), env, args.size() > 2 ? TOO_MANY_ARGS : TOO_FEW_ARGS);
-	    return MlValue(int(args[0] != args[1]));
+	    return MlValue(long(args[0] != args[1]));
     }
 
     // Is one number greater than another?
@@ -1310,7 +1310,7 @@ namespace builtin {
 
 	    if (args.size() != 2)
 		    throw MlError(MlValue(">", greater), env, args.size() > 2 ? TOO_MANY_ARGS : TOO_FEW_ARGS);
-	    return MlValue(int(args[0] > args[1]));
+	    return MlValue(long(args[0] > args[1]));
     }
 
     // Is one number less than another?
@@ -1319,7 +1319,7 @@ namespace builtin {
 
 	    if (args.size() != 2)
 		    throw MlError(MlValue("<", less), env, args.size() > 2 ? TOO_MANY_ARGS : TOO_FEW_ARGS);
-	    return MlValue(int(args[0] < args[1]));
+	    return MlValue(long(args[0] < args[1]));
     }
 
     // Is one number greater than or equal to another?
@@ -1328,7 +1328,7 @@ namespace builtin {
 
 	    if (args.size() != 2)
 		    throw MlError(MlValue(">=", greater_eq), env, args.size() > 2 ? TOO_MANY_ARGS : TOO_FEW_ARGS);
-	    return MlValue(int(args[0] >= args[1]));
+	    return MlValue(long(args[0] >= args[1]));
     }
 
     // Is one number less than or equal to another?
@@ -1337,7 +1337,7 @@ namespace builtin {
 
 	    if (args.size() != 2)
 		    throw MlError(MlValue("<=", less_eq), env, args.size() > 2 ? TOO_MANY_ARGS : TOO_FEW_ARGS);
-	    return MlValue(int(args[0] <= args[1]));
+	    return MlValue(long(args[0] <= args[1]));
     }
 
     // Get the type name of a value
@@ -1388,7 +1388,7 @@ namespace builtin {
 		    throw MlError(MlValue("index", index), env, args.size() > 2 ? TOO_MANY_ARGS : TOO_FEW_ARGS);
 
 	    std::vector<MlValue> list = args[0].as_list();
-	    int i = args[1].as_int();
+	    long i = args[1].as_int();
 	    if (list.empty() || i >= list.size())
 		    throw MlError(list, env, INDEX_OUT_OF_RANGE);
 
@@ -1403,7 +1403,7 @@ namespace builtin {
 		    throw MlError(MlValue("insert", insert), env, args.size() > 3 ? TOO_MANY_ARGS : TOO_FEW_ARGS);
 
 	    std::vector<MlValue> list = args[0].as_list();
-	    int i = args[1].as_int();
+	    long i = args[1].as_int();
 	    if (i > list.size())
 		    throw MlError(list, env, INDEX_OUT_OF_RANGE);
 
@@ -1419,7 +1419,7 @@ namespace builtin {
 		    throw MlError(MlValue("remove", remove), env, args.size() > 2 ? TOO_MANY_ARGS : TOO_FEW_ARGS);
 
 	    std::vector<MlValue> list = args[0].as_list();
-	    int i = args[1].as_int();
+	    long i = args[1].as_int();
 	    if (list.empty() || i >= list.size())
 		    throw MlError(list, env, INDEX_OUT_OF_RANGE);
 
@@ -1436,7 +1436,7 @@ namespace builtin {
 							    TOO_MANY_ARGS : TOO_FEW_ARGS
 		    );
 
-	    return MlValue(int(args[0].as_list().size()));
+	    return MlValue(long(args[0].as_list().size()));
     }
 
     // Add an item to the end of a list
@@ -1520,7 +1520,7 @@ namespace builtin {
 	    if (args.size() != 2)		// if (args.size() < 2 || args.size() > 3)
 		    throw MlError(MlValue("string-regex?", string_regex), env, args.size() > 2 ? TOO_MANY_ARGS : TOO_FEW_ARGS);
 
-	    return MlValue(regexp_search(args[0].as_string(), args[1].as_string()));
+	    return MlValue((long)regexp_search(args[0].as_string(), args[1].as_string()));
     }
 
     MlValue string_pad(std::vector<MlValue> args, MlEnvironment &env) {
@@ -1633,7 +1633,7 @@ namespace builtin {
 
 	    while (low < high) {
 		    result.push_back(low);
-		    low = low + MlValue(1);
+		    low = low + MlValue(1l);
 	    }
 	    return MlValue(result);
     }
diff --git a/ml.h b/ml.h
index 6c417eb..633203b 100644
--- a/ml.h
+++ b/ml.h
@@ -98,7 +98,7 @@ public:
     MlValue();
 
     // Constructs an integer
-    MlValue(int i);
+    MlValue(long i);
 
     // Constructs a floating point value
     MlValue(double f);
@@ -141,7 +141,7 @@ public:
     bool as_bool() const;
 
     // Get this item's integer value
-    int as_int() const;
+    long as_int() const;
 
     // Get this item's floating point value
     double as_float() const;
@@ -224,7 +224,7 @@ private:
     } type;
 
     union {
-	int i;
+	long i;
 	double f;
 	Builtin b;
     } stack_data;
diff --git a/ml_date.cpp b/ml_date.cpp
index f68a933..e6ff561 100644
--- a/ml_date.cpp
+++ b/ml_date.cpp
@@ -1,15 +1,15 @@
 
 #include "ml_date.h"
 
-int now() {
+long now() {
 	// get-universal-time
 	time_t t = std::time(0);
 	long int now = static_cast<long int>(t);
 
-	return (int) now;
+	return now;
 }
 
-std::string date_to_string(const int datetime, const std::string format) {
+std::string date_to_string(const long datetime, const std::string format) {
 	// std::locale::global(std::locale("en-US.UTF8"));
 
 	time_t timestamp = datetime;
@@ -23,16 +23,16 @@ std::string date_to_string(const int datetime, const std::string format) {
     return "invalid argument";
 }
 
-int string_to_date(const std::string &datestr, const std::string &format) {
+long string_to_date(const std::string &datestr, const std::string &format) {
 	// format for example "%d.%m.%Y";
 
 	std::istringstream in{datestr.c_str()};
 	date::sys_seconds tp;
 	in >> date::parse(format, tp);
-	return (int) tp.time_since_epoch().count();
+	return tp.time_since_epoch().count();
 }
 
-int add_to_date(const int datetime, const int quantity, const std::string &part) {
+long add_to_date(const long datetime, const long quantity, const std::string &part) {
 	// part is one of 'year', 'month', 'day', 'hour', 'minute' or 'second'
 
 	// very basic implementation, just for now - no timezones DST etc
@@ -55,5 +55,5 @@ int add_to_date(const int datetime, const int quantity, const std::string &part)
 		// TODO exception here
 	}
 
-	return (int) mktime(tm);
+	return mktime(tm);
 }
diff --git a/ml_date.h b/ml_date.h
index f6f80dd..09a3e46 100644
--- a/ml_date.h
+++ b/ml_date.h
@@ -8,12 +8,12 @@
 #include <vector>
 
 
-int now();
+long now();
 
 // TODO temporary solution before format will be implemented
-std::string date_to_string(const int datetime, const std::string format);
+std::string date_to_string(const long datetime, const std::string format);
 
-int string_to_date(const std::string &datestr, const std::string &format);
+long string_to_date(const std::string &datestr, const std::string &format);
 
-int add_to_date(const int datetime, const int quantity, const std::string &part);
+long add_to_date(const long datetime, const long quantity, const std::string &part);
 
diff --git a/ml_io.cpp b/ml_io.cpp
index 4bb161f..0fc3e7f 100644
--- a/ml_io.cpp
+++ b/ml_io.cpp
@@ -93,7 +93,7 @@ MlValue exec_system_cmd(const std::string &cmd) {
 
 	// TODO add helper function for this
 	std::vector<MlValue> lst;
-	lst.push_back(MlValue(cmd_retval));
+	lst.push_back(MlValue((long)cmd_retval));
 	lst.push_back(MlValue::string(cmd_output));
 	return lst;
 }