diff --git a/src/core/global.h b/src/core/global.h
--- a/src/core/global.h
+++ b/src/core/global.h
@@ -248,6 +248,7 @@
     ERR_CANNOT_CREATE_SLAVE = KJob::UserDefinedError + 73, ///< used by Slave::createSlave, @since 5.30
     ERR_FILE_TOO_LARGE_FOR_FAT32 = KJob::UserDefinedError + 74, ///< @since 5.54
     ERR_OWNER_DIED = KJob::UserDefinedError + 75, ///< Value used between kuiserver and views when the job owner disappears unexpectedly. It should not be emitted by slaves. @since 5.54
+    ERR_CANNOT_MKDIR_CONTAINING_SLASH = KJob::UserDefinedError + 76, ///< A specific error for the mkdir job failing due to presence of slashes in the directory names. @since 5.55
 };
 
 /**
diff --git a/src/core/job_error.cpp b/src/core/job_error.cpp
--- a/src/core/job_error.cpp
+++ b/src/core/job_error.cpp
@@ -248,6 +248,9 @@
     case KIO::ERR_FILE_TOO_LARGE_FOR_FAT32:
         result = xi18nc("@info", "Cannot transfer <filename>%1</filename> because it is too large. The destination filesystem only supports files up to 4GB", errorText);
         break;
+    case KIO::ERR_CANNOT_MKDIR_CONTAINING_SLASH:
+        result = xi18nc("@info", "Cannot create <filename>%1</filename> because slashes are not allowed in file and folder names.", errorText);
+        break;
     default:
         result = i18n("Unknown error code %1\n%2\nPlease send a full bug report at https://bugs.kde.org.",  errorCode,  errorText);
         break;
@@ -1078,6 +1081,12 @@
         solutions << i18n("Reformat the destination drive to use a filesystem that supports files that large.");
         break;
 
+    case ERR_CANNOT_MKDIR_CONTAINING_SLASH:
+        errorName = xi18nc("@info", "Cannot create <filename>%1</filename>", errorText);
+        description = xi18nc("@info", "Cannot create <filename>%1</filename> because slashes are not allowed in file and folder names.", errorText);
+        solutions << i18n("Do not use slashes in file/folder names.");
+        break;
+
     default:
         // fall back to the plain error...
         errorName = i18n("Undocumented Error");
diff --git a/src/ioslaves/file/file.cpp b/src/ioslaves/file/file.cpp
--- a/src/ioslaves/file/file.cpp
+++ b/src/ioslaves/file/file.cpp
@@ -283,6 +283,14 @@
 {
     const QString path(url.toLocalFile());
 
+#ifndef Q_OS_WIN
+    // UNIX does not allow identifiers containing /
+    if (path.contains(QLatin1Char('/'))) {
+        error(KIO::ERR_CANNOT_MKDIR_CONTAINING_SLASH, path);
+        return;
+    }
+#endif
+
     // qDebug() << path << "permission=" << permissions;
 
     // Remove existing file or symlink, if requested (#151851)