diff --git a/packages/babel-parser/src/tokenizer/index.js b/packages/babel-parser/src/tokenizer/index.js
index a0ee5badf41e..b57006ec6922 100644
--- a/packages/babel-parser/src/tokenizer/index.js
+++ b/packages/babel-parser/src/tokenizer/index.js
@@ -971,14 +971,26 @@ export default class Tokenizer extends LocationParser {
 
   readNumber(startsWithDot: boolean): void {
     const start = this.state.pos;
-    let octal = this.input.charCodeAt(start) === charCodes.digit0;
     let isFloat = false;
     let isBigInt = false;
 
     if (!startsWithDot && this.readInt(10) === null) {
       this.raise(start, "Invalid number");
     }
-    if (octal && this.state.pos == start + 1) octal = false; // number === 0
+    let octal =
+      this.state.pos - start >= 2 &&
+      this.input.charCodeAt(start) === charCodes.digit0;
+    if (octal) {
+      if (this.state.strict) {
+        this.raise(
+          start,
+          "Legacy octal literals are not allowed in strict mode",
+        );
+      }
+      if (/[89]/.test(this.input.slice(start, this.state.pos))) {
+        octal = false;
+      }
+    }
 
     let next = this.input.charCodeAt(this.state.pos);
     if (next === charCodes.dot && !octal) {
@@ -1022,18 +1034,7 @@ export default class Tokenizer extends LocationParser {
       return;
     }
 
-    let val;
-    if (isFloat) {
-      val = parseFloat(str);
-    } else if (!octal || str.length === 1) {
-      val = parseInt(str, 10);
-    } else if (this.state.strict) {
-      this.raise(start, "Invalid number");
-    } else if (/[89]/.test(str)) {
-      val = parseInt(str, 10);
-    } else {
-      val = parseInt(str, 8);
-    }
+    const val = octal ? parseInt(str, 8) : parseFloat(str);
     this.finishToken(tt.num, val);
   }
 
diff --git a/packages/babel-parser/test/fixtures/core/regression/non-octal-float-strict-mode/input.js b/packages/babel-parser/test/fixtures/core/regression/non-octal-float-strict-mode/input.js
new file mode 100644
index 000000000000..cbc4507bfeae
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/core/regression/non-octal-float-strict-mode/input.js
@@ -0,0 +1 @@
+09.5
diff --git a/packages/babel-parser/test/fixtures/core/regression/non-octal-float-strict-mode/options.json b/packages/babel-parser/test/fixtures/core/regression/non-octal-float-strict-mode/options.json
new file mode 100644
index 000000000000..956965603040
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/core/regression/non-octal-float-strict-mode/options.json
@@ -0,0 +1,4 @@
+{
+    "sourceType": "module",
+    "throws": "Legacy octal literals are not allowed in strict mode (1:0)"
+}
diff --git a/packages/babel-parser/test/fixtures/core/regression/non-octal-float/input.js b/packages/babel-parser/test/fixtures/core/regression/non-octal-float/input.js
new file mode 100644
index 000000000000..cbc4507bfeae
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/core/regression/non-octal-float/input.js
@@ -0,0 +1 @@
+09.5
diff --git a/packages/babel-parser/test/fixtures/core/regression/non-octal-float/output.json b/packages/babel-parser/test/fixtures/core/regression/non-octal-float/output.json
new file mode 100644
index 000000000000..f48f7a786775
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/core/regression/non-octal-float/output.json
@@ -0,0 +1,70 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 4,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 1,
+      "column": 4
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 4,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 1,
+        "column": 4
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ExpressionStatement",
+        "start": 0,
+        "end": 4,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 1,
+            "column": 4
+          }
+        },
+        "expression": {
+          "type": "NumericLiteral",
+          "start": 0,
+          "end": 4,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 0
+            },
+            "end": {
+              "line": 1,
+              "column": 4
+            }
+          },
+          "extra": {
+            "rawValue": 9.5,
+            "raw": "09.5"
+          },
+          "value": 9.5
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/core/regression/octal-float-fail/input.js b/packages/babel-parser/test/fixtures/core/regression/octal-float-fail/input.js
new file mode 100644
index 000000000000..80b817b29181
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/core/regression/octal-float-fail/input.js
@@ -0,0 +1 @@
+07.5
diff --git a/packages/babel-parser/test/fixtures/core/regression/octal-float-fail/options.json b/packages/babel-parser/test/fixtures/core/regression/octal-float-fail/options.json
new file mode 100644
index 000000000000..ff1ac8247e68
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/core/regression/octal-float-fail/options.json
@@ -0,0 +1,3 @@
+{
+  "throws": "Unexpected token, expected \";\" (1:2)"
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/core/uncategorised/500/options.json b/packages/babel-parser/test/fixtures/core/uncategorised/500/options.json
index ec4ea95dc9cb..45ca229c1e8e 100644
--- a/packages/babel-parser/test/fixtures/core/uncategorised/500/options.json
+++ b/packages/babel-parser/test/fixtures/core/uncategorised/500/options.json
@@ -1,3 +1,3 @@
 {
-  "throws": "Invalid number (1:33)"
+  "throws": "Legacy octal literals are not allowed in strict mode (1:33)"
 }
diff --git a/packages/babel-parser/test/fixtures/core/uncategorised/502/options.json b/packages/babel-parser/test/fixtures/core/uncategorised/502/options.json
index dd200e16e5bf..8f6c8218f747 100644
--- a/packages/babel-parser/test/fixtures/core/uncategorised/502/options.json
+++ b/packages/babel-parser/test/fixtures/core/uncategorised/502/options.json
@@ -1,3 +1,3 @@
 {
-  "throws": "Invalid number (1:36)"
+  "throws": "Legacy octal literals are not allowed in strict mode (1:36)"
 }
diff --git a/packages/babel-parser/test/fixtures/core/uncategorised/522/options.json b/packages/babel-parser/test/fixtures/core/uncategorised/522/options.json
index 3696be182d05..0b443b9bacfa 100644
--- a/packages/babel-parser/test/fixtures/core/uncategorised/522/options.json
+++ b/packages/babel-parser/test/fixtures/core/uncategorised/522/options.json
@@ -1,3 +1,3 @@
 {
-  "throws": "Invalid number (1:65)"
+  "throws": "Legacy octal literals are not allowed in strict mode (1:65)"
 }
diff --git a/packages/babel-parser/test/fixtures/core/uncategorised/550/options.json b/packages/babel-parser/test/fixtures/core/uncategorised/550/options.json
index f635fb88c5c9..5cee88d901e4 100644
--- a/packages/babel-parser/test/fixtures/core/uncategorised/550/options.json
+++ b/packages/babel-parser/test/fixtures/core/uncategorised/550/options.json
@@ -1,3 +1,3 @@
 {
-  "throws": "Invalid number (2:10)"
+  "throws": "Legacy octal literals are not allowed in strict mode (2:10)"
 }
diff --git a/packages/babel-parser/test/fixtures/core/uncategorised/552/options.json b/packages/babel-parser/test/fixtures/core/uncategorised/552/options.json
index f635fb88c5c9..5cee88d901e4 100644
--- a/packages/babel-parser/test/fixtures/core/uncategorised/552/options.json
+++ b/packages/babel-parser/test/fixtures/core/uncategorised/552/options.json
@@ -1,3 +1,3 @@
 {
-  "throws": "Invalid number (2:10)"
+  "throws": "Legacy octal literals are not allowed in strict mode (2:10)"
 }
diff --git a/packages/babel-parser/test/fixtures/es2015/uncategorised/249/options.json b/packages/babel-parser/test/fixtures/es2015/uncategorised/249/options.json
index 0f2c1bee90b0..79a05e62290e 100644
--- a/packages/babel-parser/test/fixtures/es2015/uncategorised/249/options.json
+++ b/packages/babel-parser/test/fixtures/es2015/uncategorised/249/options.json
@@ -1,3 +1,3 @@
 {
-  "throws": "Invalid number (1:21)"
+  "throws": "Legacy octal literals are not allowed in strict mode (1:21)"
 }
diff --git a/packages/babel-parser/test/fixtures/esprima/invalid-syntax/migrated_0094/options.json b/packages/babel-parser/test/fixtures/esprima/invalid-syntax/migrated_0094/options.json
index 0f2c1bee90b0..79a05e62290e 100644
--- a/packages/babel-parser/test/fixtures/esprima/invalid-syntax/migrated_0094/options.json
+++ b/packages/babel-parser/test/fixtures/esprima/invalid-syntax/migrated_0094/options.json
@@ -1,3 +1,3 @@
 {
-  "throws": "Invalid number (1:21)"
+  "throws": "Legacy octal literals are not allowed in strict mode (1:21)"
 }
diff --git a/packages/babel-parser/test/fixtures/esprima/invalid-syntax/migrated_0218/options.json b/packages/babel-parser/test/fixtures/esprima/invalid-syntax/migrated_0218/options.json
index ec4ea95dc9cb..45ca229c1e8e 100644
--- a/packages/babel-parser/test/fixtures/esprima/invalid-syntax/migrated_0218/options.json
+++ b/packages/babel-parser/test/fixtures/esprima/invalid-syntax/migrated_0218/options.json
@@ -1,3 +1,3 @@
 {
-  "throws": "Invalid number (1:33)"
+  "throws": "Legacy octal literals are not allowed in strict mode (1:33)"
 }
diff --git a/packages/babel-parser/test/fixtures/esprima/invalid-syntax/migrated_0220/options.json b/packages/babel-parser/test/fixtures/esprima/invalid-syntax/migrated_0220/options.json
index dd200e16e5bf..8f6c8218f747 100644
--- a/packages/babel-parser/test/fixtures/esprima/invalid-syntax/migrated_0220/options.json
+++ b/packages/babel-parser/test/fixtures/esprima/invalid-syntax/migrated_0220/options.json
@@ -1,3 +1,3 @@
 {
-  "throws": "Invalid number (1:36)"
+  "throws": "Legacy octal literals are not allowed in strict mode (1:36)"
 }