diff --git a/thumbnail/thumbnail.h b/thumbnail/thumbnail.h
--- a/thumbnail/thumbnail.h
+++ b/thumbnail/thumbnail.h
@@ -83,6 +83,7 @@
     QSet<QString> m_propagationDirectories;
     QString m_thumbBasePath;
     qint64 m_maxFileSize;
+    dev_t m_thumbnailDirDeviceId = 0;
 };
 
 #endif
diff --git a/thumbnail/thumbnail.cpp b/thumbnail/thumbnail.cpp
--- a/thumbnail/thumbnail.cpp
+++ b/thumbnail/thumbnail.cpp
@@ -28,6 +28,7 @@
 #ifndef Q_OS_WIN
 #include <sys/ipc.h>
 #include <sys/shm.h>
+#include <sys/stat.h>
 #include <unistd.h> // nice()
 #endif
 
@@ -77,6 +78,7 @@
 #endif
 
 #include "imagefilter.h"
+#include <KMountPoint>
 
 // Recognized metadata entries:
 // mimeType     - the mime type of the file, used for the overlay icon if any
@@ -722,6 +724,27 @@
         if (!thumbnail.load(thumbPath.absoluteFilePath(thumbName))) {
             // no cached version is available, a new thumbnail must be created
 
+            // If file is on the same filesystem as thumbnail directory, we can cache it.
+            bool allowCache = false;
+#ifdef _SYS_STAT_H
+            if (!m_thumbnailDirDeviceId) {
+                struct stat baseStat;
+                if (!lstat(QFile::encodeName(m_thumbBasePath).data(), &baseStat)) {
+                    m_thumbnailDirDeviceId = baseStat.st_dev;
+                }
+            }
+            struct stat fileStat;
+            if (m_thumbnailDirDeviceId && !lstat(QFile::encodeName(filePath).data(), &fileStat)) {
+                allowCache = m_thumbnailDirDeviceId == fileStat.st_dev;
+            }
+#endif
+            if (!allowCache) {
+                // If file is on encrypted filesystem different than thumbnail directory, we can't cache it
+                const auto mountsList = KMountPoint::currentMountPoints();
+                const auto mount =  mountsList.findByPath(filePath);
+                allowCache = !(mount->mountType() == QLatin1String("fuse.cryfs") || mount->mountType() == QLatin1String("fuse.encfs"));
+            }
+
             QSaveFile thumbnailfile(thumbPath.absoluteFilePath(thumbName));
             bool savedCorrectly = false;
             if (subCreator->create(filePath, cacheSize, cacheSize, thumbnail)) {
@@ -729,7 +752,7 @@
 
                 // The thumbnail has been created successfully. Store the thumbnail
                 // to the cache for future access.
-                if (thumbnailfile.open(QIODevice::WriteOnly | QIODevice::Truncate)) {
+                if (allowCache && thumbnailfile.open(QIODevice::WriteOnly | QIODevice::Truncate)) {
                     savedCorrectly = thumbnail.save(&thumbnailfile, "PNG");
                 }
             } else {