diff --git a/layout/base/LayoutLogging.cpp b/layout/base/LayoutLogging.cpp
index 661ddcecf5e..df4f5ab3db3 100644
--- a/layout/base/LayoutLogging.cpp
+++ b/layout/base/LayoutLogging.cpp
@@ -24,11 +24,19 @@ namespace detail {
 void LayoutLogWarning(const char* aStr, const char* aExpr,
                       const char* aFile, int32_t aLine)
 {
-  MOZ_LOG(GetLayoutLog(),
-          mozilla::LogLevel::Warning,
-          ("[%d] WARNING: %s: '%s', file %s, line %d",
-           base::GetCurrentProcId(),
-           aStr, aExpr, aFile, aLine));
+  if (aExpr) {
+    MOZ_LOG(GetLayoutLog(),
+            mozilla::LogLevel::Warning,
+            ("[%d] WARNING: %s: '%s', file %s, line %d",
+             base::GetCurrentProcId(),
+             aStr, aExpr, aFile, aLine));
+  } else {
+    MOZ_LOG(GetLayoutLog(),
+            mozilla::LogLevel::Warning,
+            ("[%d] WARNING: %s: file %s, line %d",
+             base::GetCurrentProcId(),
+             aStr, aFile, aLine));
+  }
 }
 
 } // namespace detail
diff --git a/layout/base/LayoutLogging.h b/layout/base/LayoutLogging.h
index 5da1b1124fb..377bebc9111 100644
--- a/layout/base/LayoutLogging.h
+++ b/layout/base/LayoutLogging.h
@@ -17,7 +17,7 @@ PRLogModuleInfo* GetLayoutLog();
  * Use the layout log to warn if a given condition is false.
  *
  * This is only enabled in debug builds and the logging is only displayed if
- * the environmental variable NSPR_LOG_MODULES includes "layout:2" (or higher). 
+ * the environmental variable NSPR_LOG_MODULES includes "layout:2" (or higher).
  */
 #ifdef DEBUG
 #define LAYOUT_WARN_IF_FALSE(_cond, _msg)                                  \
@@ -33,6 +33,25 @@ PRLogModuleInfo* GetLayoutLog();
   PR_END_MACRO
 #endif
 
+/**
+ * Use the layout log to emit a warning with the same format as NS_WARNING.
+ *
+ * This is only enabled in debug builds and the logging is only displayed if
+ * the environmental variable NSPR_LOG_MODULES includes "layout:2" (or higher).
+ */
+#ifdef DEBUG
+#define LAYOUT_WARNING(_msg)                                                \
+  PR_BEGIN_MACRO                                                            \
+    if (MOZ_LOG_TEST(GetLayoutLog(), mozilla::LogLevel::Warning)) {         \
+      mozilla::detail::LayoutLogWarning(_msg, nullptr, __FILE__, __LINE__); \
+    }                                                                       \
+  PR_END_MACRO
+#else
+#define LAYOUT_WARNING(_msg) \
+  PR_BEGIN_MACRO             \
+  PR_END_MACRO
+#endif
+
 namespace mozilla {
 namespace detail {