diff --git a/rtengine/imagedata.cc b/rtengine/imagedata.cc
index cedf08ca0..16b6a4c91 100644
--- a/rtengine/imagedata.cc
+++ b/rtengine/imagedata.cc
@@ -69,6 +69,15 @@ T getFromFrame(
     return {};
 }
 
+const std::string& validateUft8(const std::string& str, const std::string& on_error = "???")
+{
+    if (Glib::ustring(str).validate()) {
+        return str;
+    }
+
+    return on_error;
+}
+
 }
 
 FramesMetaData* FramesMetaData::fromFile(const Glib::ustring& fname, std::unique_ptr<RawMetaDataLocation> rml, bool firstFrameOnly)
@@ -122,7 +131,7 @@ FrameData::FrameData(rtexif::TagDirectory* frameRootDir_, rtexif::TagDirectory*
     }
 
     if (tag) {
-        make = tag->valueToString();
+        make = validateUft8(tag->valueToString());
 
         // Same dcraw treatment
         for (const auto& corp : {
@@ -158,7 +167,7 @@ FrameData::FrameData(rtexif::TagDirectory* frameRootDir_, rtexif::TagDirectory*
     tag = newFrameRootDir->findTagUpward("Model");
 
     if (tag) {
-        model = tag->valueToString();
+        model = validateUft8(tag->valueToString());
     }
 
     if (!model.empty()) {
@@ -193,14 +202,14 @@ FrameData::FrameData(rtexif::TagDirectory* frameRootDir_, rtexif::TagDirectory*
     if (model == "Unknown") {
         tag = newFrameRootDir->findTag("UniqueCameraModel");
         if (tag) {
-            model = tag->valueToString();
+            model = validateUft8(tag->valueToString());
         }
     }
 
     tag = newFrameRootDir->findTagUpward("Orientation");
 
     if (tag) {
-        orientation = tag->valueToString();
+        orientation = validateUft8(tag->valueToString());
     }
 
     // Look for Rating metadata in the following order:
@@ -310,7 +319,7 @@ FrameData::FrameData(rtexif::TagDirectory* frameRootDir_, rtexif::TagDirectory*
         }
 
         if (tag) {
-            serial = tag->valueToString();
+            serial = validateUft8(tag->valueToString());
         }
 
         // guess lens...
@@ -320,7 +329,7 @@ FrameData::FrameData(rtexif::TagDirectory* frameRootDir_, rtexif::TagDirectory*
 
         if (!make.compare(0, 8, "FUJIFILM")) {
             if (exif->getTag("LensModel")) {
-                lens = exif->getTag("LensModel")->valueToString();
+                lens = validateUft8(exif->getTag("LensModel")->valueToString());
             }
         } else if (!make.compare(0, 4, "SONY")) {
             if (iso_speed == 65535 || iso_speed == 0) {
@@ -347,9 +356,9 @@ FrameData::FrameData(rtexif::TagDirectory* frameRootDir_, rtexif::TagDirectory*
                         const rtexif::Tag* const lens_make = exif->getTag(0xA433);
                         const std::string make =
                             lens_make
-                                ? lens_make->valueToString()
+                                ? validateUft8(lens_make->valueToString())
                                 : std::string();
-                        const std::string model = lens_model->valueToString();
+                        const std::string model = validateUft8(lens_model->valueToString());
 
                         if (!model.empty()) {
                             lens = make;
@@ -382,7 +391,7 @@ FrameData::FrameData(rtexif::TagDirectory* frameRootDir_, rtexif::TagDirectory*
                     bool lensOk = false;
 
                     if (mnote->getTag("LensData")) {
-                        std::string ldata = mnote->getTag("LensData")->valueToString();
+                        std::string ldata = validateUft8(mnote->getTag("LensData")->valueToString());
                         size_t pos;
 
                         if (ldata.size() > 10 && (pos = ldata.find("Lens = ")) != Glib::ustring::npos) {
@@ -394,10 +403,10 @@ FrameData::FrameData(rtexif::TagDirectory* frameRootDir_, rtexif::TagDirectory*
                                 size_t pos = lens.find("$FL$");        // is there a placeholder for focallength?
 
                                 if (pos != Glib::ustring::npos) {               // then fill in focallength
-                                    lens = lens.replace(pos, 4, exif->getTag("FocalLength")->valueToString());
+                                    lens = lens.replace(pos, 4, validateUft8(exif->getTag("FocalLength")->valueToString()));
 
                                     if (mnote->getTag("LensType")) {
-                                        std::string ltype = mnote->getTag("LensType")->valueToString();
+                                        const std::string ltype = validateUft8(mnote->getTag("LensType")->valueToString());
 
                                         if (ltype.find("MF = Yes") != Glib::ustring::npos) { // check, whether it's a MF lens, should be always
                                             lens = lens.replace(0, 7, "MF");
@@ -416,7 +425,7 @@ FrameData::FrameData(rtexif::TagDirectory* frameRootDir_, rtexif::TagDirectory*
                     }
 
                     if (!lensOk && mnote->getTag("Lens")) {
-                        std::string ldata = mnote->getTag("Lens")->valueToString();
+                        const std::string ldata = validateUft8(mnote->getTag("Lens")->valueToString());
                         size_t i = 0, j = 0;
                         double n[4] = {0.0};
 
@@ -453,7 +462,7 @@ FrameData::FrameData(rtexif::TagDirectory* frameRootDir_, rtexif::TagDirectory*
 
                         // Look whether it's MF or AF
                         if (mnote->getTag("LensType")) {
-                            std::string ltype = mnote->getTag("LensType")->valueToString();
+                            const std::string ltype = validateUft8(mnote->getTag("LensType")->valueToString());
 
                             if (ltype.find("MF = Yes") != Glib::ustring::npos) { // check, whether it's a MF lens
                                 lens = lens.replace(0, 7, "MF");    // replace 'Unknwon' with 'MF'
@@ -478,7 +487,7 @@ FrameData::FrameData(rtexif::TagDirectory* frameRootDir_, rtexif::TagDirectory*
 
                     if (lt) {
                         if (lt->toInt()) {
-                            std::string ldata = lt->valueToString ();
+                            const std::string ldata = validateUft8(lt->valueToString());
 
                             if (ldata.size() > 1) {
                                 found = true;
@@ -499,7 +508,7 @@ FrameData::FrameData(rtexif::TagDirectory* frameRootDir_, rtexif::TagDirectory*
                         lt = mnote->findTag("LensID");
 
                         if (lt) {
-                            std::string ldata = lt->valueToString();
+                            const std::string ldata = validateUft8(lt->valueToString());
 
                             if (ldata.size() > 1) {
                                 lens = ldata;
@@ -521,7 +530,7 @@ FrameData::FrameData(rtexif::TagDirectory* frameRootDir_, rtexif::TagDirectory*
                     }
 
                     if (mnote->getTag("LensType")) {
-                        lens = mnote->getTag ("LensType")->valueToString();
+                        lens = validateUft8(mnote->getTag("LensType")->valueToString());
                         // If MakeNotes are vague, fall back to Exif LensMake and LensModel if set
                         // https://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/Pentax.html#LensType
                         if (lens == "M-42 or No Lens" || lens == "K or M Lens" || lens == "A Series Lens" || lens == "Sigma") {
@@ -548,7 +557,7 @@ FrameData::FrameData(rtexif::TagDirectory* frameRootDir_, rtexif::TagDirectory*
                     }
                 } else if (!make.compare (0, 4, "SONY") || !make.compare (0, 6, "KONICA")) {
                     if (mnote->getTag ("LensID")) {
-                        lens = mnote->getTag ("LensID")->valueToString ();
+                        lens = validateUft8(mnote->getTag("LensID")->valueToString());
                         if (lens == "Unknown") {
                             lens_from_make_and_model();
                         }
@@ -558,7 +567,7 @@ FrameData::FrameData(rtexif::TagDirectory* frameRootDir_, rtexif::TagDirectory*
                         rtexif::TagDirectory* eq = mnote->getTag("Equipment")->getDirectory();
 
                         if (eq->getTag("LensType")) {
-                            lens = eq->getTag("LensType")->valueToString();
+                            lens = validateUft8(eq->getTag("LensType")->valueToString());
                         }
                     }
                     if (lens == "Unknown") {
@@ -566,7 +575,7 @@ FrameData::FrameData(rtexif::TagDirectory* frameRootDir_, rtexif::TagDirectory*
                     }
                 } else if (!make.compare (0, 9, "Panasonic")) {
                     if (mnote->getTag ("LensType")) {
-                        std::string panalens = mnote->getTag("LensType")->valueToString();
+                        const std::string panalens = validateUft8(mnote->getTag("LensType")->valueToString());
 
                         if (panalens.find("LUMIX") != Glib::ustring::npos) {
                             lens = "Panasonic " + panalens;
@@ -576,9 +585,9 @@ FrameData::FrameData(rtexif::TagDirectory* frameRootDir_, rtexif::TagDirectory*
                     }
                 }
             } else if (exif->getTag("DNGLensInfo")) {
-                lens = exif->getTag("DNGLensInfo")->valueToString();
+                lens = validateUft8(exif->getTag("DNGLensInfo")->valueToString());
             } else if (!lens_from_make_and_model() && exif->getTag ("LensInfo")) {
-                lens = exif->getTag("LensInfo")->valueToString();
+                lens = validateUft8(exif->getTag("LensInfo")->valueToString());
             }
         }
     }
diff --git a/rtgui/exifpanel.cc b/rtgui/exifpanel.cc
index 341d0f303..3f6bbacb5 100644
--- a/rtgui/exifpanel.cc
+++ b/rtgui/exifpanel.cc
@@ -209,6 +209,9 @@ void ExifPanel::setImageData (const FramesMetaData* id)
 
 Gtk::TreeModel::Children ExifPanel::addTag (const Gtk::TreeModel::Children& root, Glib::ustring field, Glib::ustring value, rtexif::ActionCode action, bool editable)
 {
+    if (!value.validate()) {
+        value = "???";
+    }
 
     Gtk::TreeModel::Row row = * (exifTreeModel->append (root));
     row[exifColumns.action]   = action;