--- a/js/src/jit-test/tests/debug/wasm-05.js
+++ b/js/src/jit-test/tests/debug/wasm-05.js
@@ -52,16 +52,18 @@ for (let descriptor of WebAssembly.Modul
     imports[descriptor.module] = {}
     switch(descriptor.kind) {
         case "function": imports[descriptor.module][descriptor.name] = new Function(''); break;
     }
 }
 var instance = new WebAssembly.Instance(module, imports);
 `);
     var wasmScript = dbg.findScripts().filter(s => s.format == 'wasm')[0];
+    assertEq(wasmScript.startLine, 1);
+    assertEq(wasmScript.lineCount > 0, true);
     var lines = wasmScript.source.text.split('\n');
     var offsetsFound = 0;
     lines.forEach(function (l, n) {
         var offsets = wasmScript.getLineOffsets(n + 1);
         if (offsets.length < 1) return;
         assertEq(offsets.length, 1);
         assertEq(offsets[0] > 0, true);
         offsetsFound++;
@@ -97,15 +99,17 @@ function getWasmScriptAfterDebuggerAttac
     // Attaching after wasm instance is created.
     dbg.addDebuggee(sandbox);
     var wasmScript = dbg.findScripts().filter(s => s.format == 'wasm')[0];
     return wasmScript;
 }
 
 var wasmScript1 = getWasmScriptAfterDebuggerAttached('(module (func (nop)))');
 var wasmLines1 = wasmScript1.source.text.split('\n');
+assertEq(wasmScript1.startLine, 1);
+assertEq(wasmScript1.lineCount, 0);
 assertEq(wasmLines1.every((l, n) => wasmScript1.getLineOffsets(n + 1).length == 0), true);
 
 // Checking that we must not resolve any location for any offset in a wasm
 // instance which debug mode was not enabled.
 var wasmScript2 = getWasmScriptAfterDebuggerAttached('(module (func (nop)))');
 for (var i = wasmTextToBinary('(module (func (nop)))').length - 1; i >= 0; i--)
     assertThrowsInstanceOf(() => wasmScript2.getOffsetLocation(i), Error);

new file mode 100644
--- /dev/null
+++ b/js/src/jit-test/tests/debug/wasm-09.js
@@ -0,0 +1,35 @@
+// |jit-test| test-also-wasm-baseline
+// Tests debugEnabled state of wasm when allowUnobservedAsmJS == true.
+
+load(libdir + "asserts.js");
+
+if (!wasmIsSupported())
+     quit();
+
+// Checking that there are no offsets are present in a wasm instance script for
+// which debug mode was not enabled.
+function getWasmScriptWithoutAllowUnobservedAsmJS(wast) {
+    var sandbox = newGlobal('');
+    var dbg = new Debugger();
+    dbg.allowUnobservedAsmJS = true;
+    dbg.addDebuggee(sandbox);
+    sandbox.eval(`
+        var wasm = wasmTextToBinary('${wast}');
+        var m = new WebAssembly.Instance(new WebAssembly.Module(wasm));
+    `);
+    // Attaching after wasm instance is created.
+    var wasmScript = dbg.findScripts().filter(s => s.format == 'wasm')[0];
+    return wasmScript;
+}
+
+var wasmScript1 = getWasmScriptWithoutAllowUnobservedAsmJS('(module (func (nop)))');
+var wasmLines1 = wasmScript1.source.text.split('\n');
+assertEq(wasmScript1.startLine, 1);
+assertEq(wasmScript1.lineCount, 0);
+assertEq(wasmLines1.every((l, n) => wasmScript1.getLineOffsets(n + 1).length == 0), true);
+
+// Checking that we must not resolve any location for any offset in a wasm
+// instance which debug mode was not enabled.
+var wasmScript2 = getWasmScriptWithoutAllowUnobservedAsmJS('(module (func (nop)))');
+for (var i = wasmTextToBinary('(module (func (nop)))').length - 1; i >= 0; i--)
+    assertThrowsInstanceOf(() => wasmScript2.getOffsetLocation(i), Error);

--- a/js/src/vm/Debugger.cpp
+++ b/js/src/vm/Debugger.cpp
@@ -5672,17 +5672,17 @@ struct DebuggerScriptGetLineCountMatcher
     using ReturnType = bool;
 
     ReturnType match(HandleScript script) {
         totalLines = double(GetScriptLineExtent(script));
         return true;
     }
     ReturnType match(Handle<WasmInstanceObject*> wasmInstance) {
         uint32_t result;
-        if (wasmInstance->instance().code().totalSourceLines(cx_, &result))
+        if (!wasmInstance->instance().code().totalSourceLines(cx_, &result))
             return false;
         totalLines = double(result);
         return true;
     }
 };
 
 static bool
 DebuggerScript_getLineCount(JSContext* cx, unsigned argc, Value* vp)

--- a/js/src/wasm/WasmCode.cpp
+++ b/js/src/wasm/WasmCode.cpp
@@ -859,22 +859,24 @@ Code::getOffsetLocation(JSContext* cx, u
     *lineno = loc.lineno + experimentalWarningLinesCount;
     *column = loc.column;
     return true;
 }
 
 bool
 Code::totalSourceLines(JSContext* cx, uint32_t* count)
 {
+    *count = 0;
+    if (!metadata_->debugEnabled)
+        return true;
+
     if (!ensureSourceMap(cx))
         return false;
 
-    if (!maybeSourceMap_)
-        *count = 0;
-    else
+    if (maybeSourceMap_)
         *count = maybeSourceMap_->totalLines() + experimentalWarningLinesCount;
     return true;
 }
 
 bool
 Code::stepModeEnabled(uint32_t funcIndex) const
 {
     return stepModeCounters_.initialized() && stepModeCounters_.lookup(funcIndex);