diff --git a/lib/VM/JSLib/JSONLexer.cpp b/lib/VM/JSLib/JSONLexer.cpp
index 66d6b9490b7..51189279679 100644
--- a/lib/VM/JSLib/JSONLexer.cpp
+++ b/lib/VM/JSLib/JSONLexer.cpp
@@ -195,6 +195,13 @@ ExecutionStatus JSONLexer<Kind>::scanNumber() {
     }
   }
 
+  // The integer part cannot start with 0, unless it's 0.
+  if (*iter_.cur == '0') {
+    ++iter_.cur;
+    if (LLVM_UNLIKELY(hasChar() && *iter_.cur >= '0' && *iter_.cur <= '9'))
+      return errorWithChar(u"Unexpected character in number: ", *iter_.cur);
+  }
+
   bool isTrivialInteger = true;
   uint64_t integer = 0;
   constexpr uint64_t kFirstIntThatCanOverflow = (UINT64_MAX - 9) / 10;
@@ -221,16 +228,6 @@ ExecutionStatus JSONLexer<Kind>::scanNumber() {
     numRef = iter_.cur.endCapture();
   }
 
-  // Check for illegal leading 0.
-  size_t len = numRef.size();
-  assert(len > 0 && "scanNumber must be called on a number-looking char");
-  if (LLVM_UNLIKELY(
-          numRef[0] == '0' && len > 1 && numRef[1] >= '0' &&
-          numRef[1] <= '9')) {
-    // The integer part cannot start with 0, unless it's 0.
-    return errorWithChar(u"Unexpected character in number: ", numRef[1]);
-  }
-
   if (isTrivialInteger) {
     token_.setNumber((double)integer * multiplier);
     return ExecutionStatus::RETURNED;
diff --git a/test/hermes/json.js b/test/hermes/json.js
index e5755693761..55b1363534d 100644
--- a/test/hermes/json.js
+++ b/test/hermes/json.js
@@ -61,6 +61,24 @@ function parse(json) {
 }
 parse("015");
 //CHECK-NEXT: SyntaxError: JSON Parse error: Unexpected character in number: 1
+parse("-015");
+//CHECK-NEXT: SyntaxError: JSON Parse error: Unexpected character in number: 1
+parse("-00");
+//CHECK-NEXT: SyntaxError: JSON Parse error: Unexpected character in number: 0
+parse("[-01.5]");
+//CHECK-NEXT: SyntaxError: JSON Parse error: Unexpected character in number: 1
+print(1 / JSON.parse("-0"), JSON.parse("-0.5"), JSON.parse("[-10]")[0]);
+//CHECK-NEXT: -Infinity -0.5 -10
+// A non-ASCII character in the input makes JSON.parse use the UTF-16 lexer.
+parse("[\"\u4f60\", 015]");
+//CHECK-NEXT: SyntaxError: JSON Parse error: Unexpected character in number: 1
+parse("[\"\u4f60\", -015]");
+//CHECK-NEXT: SyntaxError: JSON Parse error: Unexpected character in number: 1
+parse("[\"\u4f60\", -00]");
+//CHECK-NEXT: SyntaxError: JSON Parse error: Unexpected character in number: 0
+var u = JSON.parse("[\"\u4f60\", -0, -0.5, -10]");
+print(1 / u[1], u[2], u[3]);
+//CHECK-NEXT: -Infinity -0.5 -10
 parse("+5");
 //CHECK-NEXT: SyntaxError: JSON Parse error: Unexpected character: +
 parse("-");