diff --git a/intl/hyphenation/glue/nsHyphenator.cpp b/intl/hyphenation/glue/nsHyphenator.cpp
index dbba68ca26ce..96faea1a816e 100644
--- a/intl/hyphenation/glue/nsHyphenator.cpp
+++ b/intl/hyphenation/glue/nsHyphenator.cpp
@@ -10,6 +10,7 @@
 #include "mozilla/ipc/SharedMemoryHandle.h"
 #include "mozilla/ipc/SharedMemoryMapping.h"
 #include "nsContentUtils.h"
+#include "nsEscape.h"
 #include "nsIChannel.h"
 #include "nsIFile.h"
 #include "nsIFileURL.h"
@@ -274,6 +275,9 @@ nsHyphenator::nsHyphenator(nsIURI* aURI, bool aHyphenateCapitalized)
       path.Cut(0, 1);
     }
 #endif
+    // In case of %-escaped spaces or other "special" chars in the path,
+    // we need the unescaped version to pass to mapped_hyph_load_dictionary.
+    NS_UnescapeURL(path);
     if (precompiled) {
       // If the file is compiled, we can just map it directly.
       UniquePtr<const HyphDic> dic(mapped_hyph_load_dictionary(path.get()));