diff --git a/src/lexer/mod.rs b/src/lexer/mod.rs
index afbbee4d0d9..e60dbbe8ec9 100644
--- a/src/lexer/mod.rs
+++ b/src/lexer/mod.rs
@@ -7,6 +7,9 @@ use self::ptr::Ptr;
 mod classes;
 use self::classes::*;
 
+mod numbers;
+use self::numbers::scan_number;
+
 pub fn next_token(text: &str) -> Token {
     assert!(!text.is_empty());
     let mut ptr = Ptr::new(text);
@@ -50,69 +53,6 @@ fn scan_ident(c: char, ptr: &mut Ptr) -> SyntaxKind {
     IDENT
 }
 
-fn scan_number(c: char, ptr: &mut Ptr) -> SyntaxKind {
-    if c == '0' {
-        match ptr.next().unwrap_or('\0') {
-            'b' | 'o' => {
-                ptr.bump();
-                scan_digits(ptr, false);
-            }
-            'x' => {
-                ptr.bump();
-                scan_digits(ptr, true);
-            }
-            '0'...'9' | '_' | '.' | 'e' | 'E' => {
-                scan_digits(ptr, true);
-            }
-            _ => return INT_NUMBER,
-        }
-    } else {
-        scan_digits(ptr, false);
-    }
-
-    // might be a float, but don't be greedy if this is actually an
-    // integer literal followed by field/method access or a range pattern
-    // (`0..2` and `12.foo()`)
-    if ptr.next_is('.') && !(ptr.nnext_is('.') || ptr.nnext_is_p(is_ident_start)) {
-        // might have stuff after the ., and if it does, it needs to start
-        // with a number
-        ptr.bump();
-        scan_digits(ptr, false);
-        scan_float_exponent(ptr);
-        return FLOAT_NUMBER;
-    }
-    // it might be a float if it has an exponent
-    if ptr.next_is('e') || ptr.next_is('E') {
-        scan_float_exponent(ptr);
-        return FLOAT_NUMBER;
-    }
-    INT_NUMBER
-}
-
-fn scan_digits(ptr: &mut Ptr, allow_hex: bool) {
-    while let Some(c) = ptr.next() {
-        match c {
-            '_' | '0'...'9' => {
-                ptr.bump();
-            }
-            'a'...'f' | 'A' ... 'F' if allow_hex => {
-                ptr.bump();
-            }
-            _ => return
-        }
-    }
-}
-
-fn scan_float_exponent(ptr: &mut Ptr) {
-    if ptr.next_is('e') || ptr.next_is('E') {
-        ptr.bump();
-        if ptr.next_is('-') || ptr.next_is('+') {
-            ptr.bump();
-        }
-        scan_digits(ptr, false);
-    }
-}
-
 fn string_literal_start(c: char, c1: Option<char>, c2: Option<char>) -> bool {
     match (c, c1, c2) {
         ('r', Some('"'), _) |
diff --git a/src/lexer/numbers.rs b/src/lexer/numbers.rs
new file mode 100644
index 00000000000..4c7edfe1ccb
--- /dev/null
+++ b/src/lexer/numbers.rs
@@ -0,0 +1,68 @@
+use lexer::ptr::Ptr;
+use lexer::classes::*;
+
+use {SyntaxKind};
+use syntax_kinds::*;
+
+pub(crate) fn scan_number(c: char, ptr: &mut Ptr) -> SyntaxKind {
+    if c == '0' {
+        match ptr.next().unwrap_or('\0') {
+            'b' | 'o' => {
+                ptr.bump();
+                scan_digits(ptr, false);
+            }
+            'x' => {
+                ptr.bump();
+                scan_digits(ptr, true);
+            }
+            '0'...'9' | '_' | '.' | 'e' | 'E' => {
+                scan_digits(ptr, true);
+            }
+            _ => return INT_NUMBER,
+        }
+    } else {
+        scan_digits(ptr, false);
+    }
+
+    // might be a float, but don't be greedy if this is actually an
+    // integer literal followed by field/method access or a range pattern
+    // (`0..2` and `12.foo()`)
+    if ptr.next_is('.') && !(ptr.nnext_is('.') || ptr.nnext_is_p(is_ident_start)) {
+        // might have stuff after the ., and if it does, it needs to start
+        // with a number
+        ptr.bump();
+        scan_digits(ptr, false);
+        scan_float_exponent(ptr);
+        return FLOAT_NUMBER;
+    }
+    // it might be a float if it has an exponent
+    if ptr.next_is('e') || ptr.next_is('E') {
+        scan_float_exponent(ptr);
+        return FLOAT_NUMBER;
+    }
+    INT_NUMBER
+}
+
+fn scan_digits(ptr: &mut Ptr, allow_hex: bool) {
+    while let Some(c) = ptr.next() {
+        match c {
+            '_' | '0'...'9' => {
+                ptr.bump();
+            }
+            'a'...'f' | 'A' ... 'F' if allow_hex => {
+                ptr.bump();
+            }
+            _ => return
+        }
+    }
+}
+
+fn scan_float_exponent(ptr: &mut Ptr) {
+    if ptr.next_is('e') || ptr.next_is('E') {
+        ptr.bump();
+        if ptr.next_is('-') || ptr.next_is('+') {
+            ptr.bump();
+        }
+        scan_digits(ptr, false);
+    }
+}
diff --git a/tests/data/lexer/0004_number.rs b/tests/data/lexer/0004_number.rs
index af53ff2cd13..0c0d3762703 100644
--- a/tests/data/lexer/0004_number.rs
+++ b/tests/data/lexer/0004_number.rs
@@ -5,3 +5,4 @@
 0e+1
 0.e+1
 0.0E-2
+0___0.10000____0000e+111__
\ No newline at end of file
diff --git a/tests/data/lexer/0004_number.txt b/tests/data/lexer/0004_number.txt
index 7dedd2cacb3..94fe0302d6b 100644
--- a/tests/data/lexer/0004_number.txt
+++ b/tests/data/lexer/0004_number.txt
@@ -60,3 +60,4 @@ INT_NUMBER 1 "1"
 WHITESPACE 1 "\n"
 FLOAT_NUMBER 6 "0.0E-2"
 WHITESPACE 1 "\n"
+FLOAT_NUMBER 26 "0___0.10000____0000e+111__"