--- a/image/ImageFactory.cpp
+++ b/image/ImageFactory.cpp
@@ -91,17 +91,18 @@ ImageFactory::CreateImage(nsIRequest* aR
 
   // Compute the image's initialization flags.
   uint32_t imageFlags = ComputeImageFlags(aURI, aMimeType, aIsMultiPart);
 
 #ifdef DEBUG
   // Record the image load for startup performance testing.
   if (NS_IsMainThread()) {
     nsCOMPtr<nsIObserverService> obs = services::GetObserverService();
-    if (NS_WARN_IF(obs)) {
+    NS_WARNING_ASSERTION(obs, "Can't get an observer service handle");
+    if (obs) {
       nsAutoCString spec;
       aURI->GetSpec(spec);
       obs->NotifyObservers(nullptr, "image-loading", NS_ConvertUTF8toUTF16(spec).get());
     }
   }
 #endif
 
   // Select the type of image to create based on MIME type.

--- a/image/RasterImage.cpp
+++ b/image/RasterImage.cpp
@@ -1394,17 +1394,18 @@ RasterImage::DrawInternal(DrawableSurfac
   gfxContextMatrixAutoSaveRestore saveMatrix(aContext);
   ImageRegion region(aRegion);
   bool frameIsFinished = aSurface->IsFinished();
 
 #ifdef DEBUG
   // Record the image drawing for startup performance testing.
   if (NS_IsMainThread()) {
     nsCOMPtr<nsIObserverService> obs = services::GetObserverService();
-    if (NS_WARN_IF(obs)) {
+    NS_WARNING_ASSERTION(obs, "Can't get an observer service handle");
+    if (obs) {
       nsCOMPtr<nsIURI> imageURI = mURI->ToIURI();
       nsAutoCString spec;
       imageURI->GetSpec(spec);
       obs->NotifyObservers(nullptr, "image-drawing", NS_ConvertUTF8toUTF16(spec).get());
     }
   }
 #endif
 

--- a/image/VectorImage.cpp
+++ b/image/VectorImage.cpp
@@ -1024,17 +1024,18 @@ VectorImage::Show(gfxDrawable* aDrawable
                              SurfaceFormat::B8G8R8A8,
                              aParams.samplingFilter,
                              aParams.flags, aParams.opacity);
 
 #ifdef DEBUG
   // Record the image drawing for startup performance testing.
   if (NS_IsMainThread()) {
     nsCOMPtr<nsIObserverService> obs = services::GetObserverService();
-    if (NS_WARN_IF(obs)) {
+    NS_WARNING_ASSERTION(obs, "Can't get an observer service handle");
+    if (obs) {
       nsCOMPtr<nsIURI> imageURI = mURI->ToIURI();
       nsAutoCString spec;
       imageURI->GetSpec(spec);
       obs->NotifyObservers(nullptr, "image-drawing", NS_ConvertUTF8toUTF16(spec).get());
     }
   }
 #endif