diff --git a/compiler/lexer/lexer.go b/compiler/lexer/lexer.go
index a41d96133..99df9eb23 100644
--- a/compiler/lexer/lexer.go
+++ b/compiler/lexer/lexer.go
@@ -264,12 +264,29 @@ func (l *Lexer) resetNosymbol() {
 
 }
 
+// prevent double underscores and underscore at the end such as 1__2, 3_
+func (l *Lexer) checkNumberError() bool {
+
+	return l.ch == '_' && (l.readPosition >= len(l.input) || !isDigit(l.input[l.readPosition]))
+
+}
+
 func (l *Lexer) readNumber() []rune {
-	position := l.position
-	for isDigit(l.ch) {
+	var input []rune
+
+	for isDigit(l.ch) || l.ch == '_' {
+
+		if isDigit(l.ch) {
+			input = append(input, l.ch)
+		}
+
+		if l.checkNumberError() {
+			return input
+		}
+
 		l.readChar()
 	}
-	return l.input[position:l.position]
+	return input
 }
 
 func (l *Lexer) readIdentifier() []rune {
diff --git a/compiler/lexer/lexer_test.go b/compiler/lexer/lexer_test.go
index 1864193e2..f9709c83a 100644
--- a/compiler/lexer/lexer_test.go
+++ b/compiler/lexer/lexer_test.go
@@ -125,6 +125,8 @@ func TestNextToken(t *testing.T) {
 	'\"string\"'
 	"\'string\'"
 	'\'string\''
+     1_23
+     12_3.45_6
 	`
 
 	tests := []struct {
@@ -438,8 +440,11 @@ func TestNextToken(t *testing.T) {
 		{token.String, "\\\"string\\\"", 116},
 		{token.String, "'string'", 117},
 		{token.String, "'string'", 118},
-
-		{token.EOF, "", 119},
+		{token.Int, "123", 119},
+		{token.Int, "123", 120},
+		{token.Dot, ".", 120},
+		{token.Int, "456", 120},
+		{token.EOF, "", 121},
 	}
 	l := New(input)
 
diff --git a/vm/float_test.go b/vm/float_test.go
index 27f4423b5..68878692c 100644
--- a/vm/float_test.go
+++ b/vm/float_test.go
@@ -266,3 +266,38 @@ func TestFloatZeroDivisionFail(t *testing.T) {
 		v.checkSP(t, i, 1)
 	}
 }
+
+func TestFloatWithWrongUnderscore(t *testing.T) {
+	testsFail := []errorTestCase{
+		{`1._2`, "UndefinedMethodError: Undefined Method '_2' for 1", 1},
+		{`1.2_`, "UndefinedMethodError: Undefined Method '_' for <Instance of: Object>", 1},
+	}
+	for i, tt := range testsFail {
+		v := initTestVM()
+		evaluated := v.testEval(t, tt.input, getFilename())
+		checkErrorMsg(t, i, evaluated, tt.expected)
+		v.checkCFP(t, i, tt.expectedCFP)
+		v.checkSP(t, i, 1)
+	}
+}
+
+func TestFloatWithCorrectUnderscore(t *testing.T) {
+
+	tests := []struct {
+		input    string
+		expected interface{}
+	}{
+		{`1_2.34`, 12.34},
+		{`12.3_4`, 12.34},
+		{`1_2.3_4`, 12.34},
+		{`1_2_3.4_5_6`, 123.456},
+	}
+
+	for i, tt := range tests {
+		v := initTestVM()
+		evaluated := v.testEval(t, tt.input, getFilename())
+		verifyExpected(t, i, evaluated, tt.expected)
+		v.checkCFP(t, i, 0)
+		v.checkSP(t, i, 1)
+	}
+}
diff --git a/vm/integer_test.go b/vm/integer_test.go
index e8dfe1c34..b2e4a30bd 100644
--- a/vm/integer_test.go
+++ b/vm/integer_test.go
@@ -390,3 +390,41 @@ func TestIntegerZeroDivisionFail(t *testing.T) {
 		v.checkSP(t, i, 1)
 	}
 }
+
+func TestIntegerWithWrongUnderscore(t *testing.T) {
+	testsFail := []errorTestCase{
+		{`1_`, "UndefinedMethodError: Undefined Method '_' for <Instance of: Object>", 1},
+		{`1__2`, "UndefinedMethodError: Undefined Method '__2' for <Instance of: Object>", 1},
+		{`_1`, "UndefinedMethodError: Undefined Method '_1' for <Instance of: Object>", 1},
+	}
+	for i, tt := range testsFail {
+		v := initTestVM()
+		evaluated := v.testEval(t, tt.input, getFilename())
+		checkErrorMsg(t, i, evaluated, tt.expected)
+		v.checkCFP(t, i, tt.expectedCFP)
+		v.checkSP(t, i, 1)
+	}
+
+}
+
+func TestIntegerWithCorrectUnderscore(t *testing.T) {
+
+	tests := []struct {
+		input    string
+		expected interface{}
+	}{
+		{`1_234`, 1234},
+		{`1_2_34`, 1234},
+		{`1_23_4`, 1234},
+		{`1_2_3_4`, 1234},
+	}
+
+	for i, tt := range tests {
+		v := initTestVM()
+		evaluated := v.testEval(t, tt.input, getFilename())
+		verifyExpected(t, i, evaluated, tt.expected)
+		v.checkCFP(t, i, 0)
+		v.checkSP(t, i, 1)
+	}
+
+}