diff --git a/src/kits/tracker/Model.cpp b/src/kits/tracker/Model.cpp
index 053753574d..745655f4f4 100644
--- a/src/kits/tracker/Model.cpp
+++ b/src/kits/tracker/Model.cpp
@@ -1281,7 +1281,24 @@ Model::Mimeset(bool force)
 	opener.OpenNode();
 	AttrChanged(NULL);
 
-	return !oldType.ICompare(MimeType());
+	return oldType.ICompare(MimeType()) != 0;
+}
+
+
+void
+Model::SniffMimeIfNeeded()
+{
+	if (fMimeType != B_FILE_MIMETYPE)
+		return;
+
+	BVolume volume(fStatBuf.st_dev);
+	if (volume.InitCheck() == B_OK && !volume.KnowsMime()) {
+		BMimeType mimeType;
+		if (BMimeType::GuessMimeType(&fEntryRef, &mimeType) == B_OK)
+			fMimeType = mimeType.Type();
+	}
+
+	return;
 }
 
 
diff --git a/src/kits/tracker/Model.h b/src/kits/tracker/Model.h
index cda33cfb1a..9b7b34f5b0 100644
--- a/src/kits/tracker/Model.h
+++ b/src/kits/tracker/Model.h
@@ -208,6 +208,9 @@ public:
 
 	bool Mimeset(bool force);
 		// returns true if mime type changed
+	void SniffMimeIfNeeded();
+		// if the filesystem does not support MIME, sets fMimeType using the MIME sniffer;
+		// makes no attempt to write the file's MIME attribute
 
 	bool HasLocalizedName() const;
 
diff --git a/src/kits/tracker/OpenWithWindow.cpp b/src/kits/tracker/OpenWithWindow.cpp
index 48464c065e..4c3f433f9a 100644
--- a/src/kits/tracker/OpenWithWindow.cpp
+++ b/src/kits/tracker/OpenWithWindow.cpp
@@ -617,6 +617,7 @@ AddOneRefSignatures(const entry_ref* ref, void* castToIterator)
 	Model model(ref, true, true);
 	if (model.InitCheck() != B_OK)
 		return NULL;
+	model.SniffMimeIfNeeded();
 
 	BString mimeType(model.MimeType());
 
@@ -1586,6 +1587,7 @@ SearchForSignatureEntryList::Relation(const BMessage* entriesToOpen,
 		Model model(&ref, true, true);
 		if (model.InitCheck())
 			continue;
+		model.SniffMimeIfNeeded();
 
 		int32 result = Relation(&model, applicationModel);
 		if (result != kNoRelation) {
@@ -1626,6 +1628,7 @@ SearchForSignatureEntryList::RelationDescription(const BMessage* entriesToOpen,
 		Model model(&ref, true, true);
 		if (model.InitCheck())
 			continue;
+		model.SniffMimeIfNeeded();
 
 		BMimeType mimeType;
 		int32 result = Relation(&model, applicationModel);
diff --git a/src/kits/tracker/Tracker.cpp b/src/kits/tracker/Tracker.cpp
index 7612a51d04..c11b1f9cd5 100644
--- a/src/kits/tracker/Tracker.cpp
+++ b/src/kits/tracker/Tracker.cpp
@@ -1171,6 +1171,7 @@ TTracker::OpenInfoWindows(BMessage* message)
 				wind->Activate();
 				delete model;
 			} else {
+				model->SniffMimeIfNeeded();
 				wind = new BInfoWindow(model, index, &fWindowList);
 				wind->PostMessage(kRestoreState);
 			}