diff --git a/lib/propmangle.js b/lib/propmangle.js
index 4e43bb63..b6222990 100644
--- a/lib/propmangle.js
+++ b/lib/propmangle.js
@@ -46,6 +46,9 @@
 function find_builtins() {
     // NaN will be included due to Number.NaN
     var a = [
+        "null",
+        "true",
+        "false",
         "Infinity",
         "-Infinity",
         "undefined",
@@ -159,7 +162,7 @@ function mangle_properties(ast, options) {
         if (options.only_cache) {
             return cache.props.has(name);
         }
-        if (/^[0-9.]+$/.test(name)) return false;
+        if (/^-?[0-9]+(\.[0-9]+)?(e[+-][0-9]+)?$/.test(name)) return false;
         return true;
     }
 
diff --git a/test/compress/issue-1770.js b/test/compress/issue-1770.js
index 9008c6f4..c6f172d2 100644
--- a/test/compress/issue-1770.js
+++ b/test/compress/issue-1770.js
@@ -7,6 +7,9 @@ mangle_props: {
             Infinity: 3,
             "-Infinity": 4,
             "-0": 5,
+            null: 6,
+            0x25: 7,
+            1e100: 8,
         };
         console.log(
             obj[void 0],
@@ -23,7 +26,16 @@ mangle_props: {
             obj["-Infinity"],
             obj[-0],
             obj[-""],
-            obj["-0"]
+            obj["-0"],
+            obj[null],
+            obj["null"],
+            obj[0x25],
+            obj["0x25"],
+            obj[37],
+            obj["37"],
+            obj[1e100],
+            obj["1e100"],
+            obj["1e+100"]
         );
     }
     expect: {
@@ -32,7 +44,10 @@ mangle_props: {
             NaN: 2,
             Infinity: 3,
             "-Infinity": 4,
-            a: 5,
+            "-0": 5,
+            null: 6,
+            37: 7,
+            1e100: 8,
         };
         console.log(
             obj[void 0],
@@ -49,10 +64,19 @@ mangle_props: {
             obj["-Infinity"],
             obj[-0],
             obj[-""],
-            obj["a"]
+            obj["-0"],
+            obj[null],
+            obj["null"],
+            obj[37],
+            obj["a"],
+            obj[37],
+            obj["37"],
+            obj[1e100],
+            obj["b"],
+            obj["1e+100"]
         );
     }
-    expect_stdout: "1 1 1 2 2 2 3 3 3 4 4 4 undefined undefined 5"
+    expect_stdout: "1 1 1 2 2 2 3 3 3 4 4 4 undefined undefined 5 6 6 7 undefined 7 7 8 undefined 8"
 }
 
 identifier: {
@@ -156,35 +180,35 @@ identifier: {
             D: 30,
             F: 31,
             G: 32,
-            H: 33,
-            I: 34,
-            J: 35,
-            K: 36,
-            L: 37,
-            M: 38,
-            N: 39,
-            O: 40,
-            P: 41,
-            Q: 42,
-            R: 43,
-            S: 44,
-            T: 45,
-            U: 46,
-            V: 47,
-            W: 48,
-            X: 49,
-            Y: 50,
-            Z: 51,
-            $: 52,
-            _: 53,
-            aa: 54,
-            ba: 55,
-            ca: 56,
-            da: 57,
-            ea: 58,
-            fa: 59,
-            ga: 60,
-            ha: 61
+            false: 33,
+            null: 34,
+            true: 35,
+            H: 36,
+            I: 37,
+            J: 38,
+            K: 39,
+            L: 40,
+            M: 41,
+            N: 42,
+            O: 43,
+            P: 44,
+            Q: 45,
+            R: 46,
+            S: 47,
+            T: 48,
+            U: 49,
+            V: 50,
+            W: 51,
+            X: 52,
+            Y: 53,
+            Z: 54,
+            $: 55,
+            _: 56,
+            aa: 57,
+            ba: 58,
+            ca: 59,
+            da: 60,
+            ea: 61,
         };
     }
 }