diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/debug/surfaces-offsets.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/debug/surfaces-offsets.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,37 @@
+// Invalid offsets result in exceptions, not bogus results.
+
+load(libdir + "asserts.js");
+
+var g = newGlobal();
+var dbg = Debugger(g);
+var hits;
+dbg.onDebuggerStatement = function (frame) {
+    assertEq(frame.script.getOffsetLine(frame.offset), g.line);
+    assertThrowsInstanceOf(function () { frame.script.getOffsetLine(String(frame.offset)); }, Error);
+    assertThrowsInstanceOf(function () { frame.script.getOffsetLine(Object(frame.offset)); }, Error);
+
+    assertThrowsInstanceOf(function () { frame.script.getOffsetLine(-1); }, Error);
+    assertThrowsInstanceOf(function () { frame.script.getOffsetLine(1000000); }, Error);
+    assertThrowsInstanceOf(function () { frame.script.getOffsetLine(0.25); }, Error);
+    assertThrowsInstanceOf(function () { frame.script.getOffsetLine(+Infinity); }, Error);
+    assertThrowsInstanceOf(function () { frame.script.getOffsetLine(-Infinity); }, Error);
+    assertThrowsInstanceOf(function () { frame.script.getOffsetLine(NaN); }, Error);
+
+    assertThrowsInstanceOf(function () { frame.script.getOffsetLine(false); }, Error);
+    assertThrowsInstanceOf(function () { frame.script.getOffsetLine(true); }, Error);
+    assertThrowsInstanceOf(function () { frame.script.getOffsetLine(undefined); }, Error);
+    assertThrowsInstanceOf(function () { frame.script.getOffsetLine(); }, Error);
+
+    // We assume that at least one whole number between 0 and frame.offset is invalid.
+    assertThrowsInstanceOf(
+        function () {
+            for (var i = 0; i < frame.offset; i++)
+                frame.script.getOffsetLine(i);
+        },
+        Error);
+
+    hits++;
+};
+
+hits = 0;
+g.eval("var line = new Error().lineNumber; debugger;");