diff --git a/annif/analyzer/simplemma.py b/annif/analyzer/simplemma.py
index e549a2585..3e1536882 100644
--- a/annif/analyzer/simplemma.py
+++ b/annif/analyzer/simplemma.py
@@ -2,7 +2,7 @@
 
 from __future__ import annotations
 
-import simplemma
+import annif.simplemma_util
 
 from . import analyzer
 
@@ -15,4 +15,4 @@ def __init__(self, param: str, **kwargs) -> None:
         super().__init__(**kwargs)
 
     def _normalize_word(self, word: str) -> str:
-        return simplemma.lemmatize(word, lang=self.lang)
+        return annif.simplemma_util.lemmatizer.lemmatize(word, lang=self.lang)
diff --git a/annif/simplemma_util.py b/annif/simplemma_util.py
new file mode 100644
index 000000000..4a8b8a1e6
--- /dev/null
+++ b/annif/simplemma_util.py
@@ -0,0 +1,17 @@
+"""Wrapper code for using Simplemma functionality in Annif"""
+
+from typing import Tuple, Union
+
+from simplemma import LanguageDetector, Lemmatizer
+from simplemma.strategies import DefaultStrategy
+from simplemma.strategies.dictionaries import DefaultDictionaryFactory
+
+LANG_CACHE_SIZE = 5  # How many language dictionaries to keep in memory at once (max)
+
+_dictionary_factory = DefaultDictionaryFactory(cache_max_size=LANG_CACHE_SIZE)
+_lemmatization_strategy = DefaultStrategy(dictionary_factory=_dictionary_factory)
+lemmatizer = Lemmatizer(lemmatization_strategy=_lemmatization_strategy)
+
+
+def get_language_detector(lang: Union[str, Tuple[str, ...]]) -> LanguageDetector:
+    return LanguageDetector(lang, lemmatization_strategy=_lemmatization_strategy)
diff --git a/annif/transform/langfilter.py b/annif/transform/langfilter.py
index f7c985485..e5cf8fdfe 100644
--- a/annif/transform/langfilter.py
+++ b/annif/transform/langfilter.py
@@ -5,9 +5,8 @@
 
 from typing import TYPE_CHECKING
 
-from simplemma.langdetect import in_target_language
-
 import annif
+import annif.simplemma_util
 
 from . import transform
 
@@ -31,6 +30,9 @@ def __init__(
         self.text_min_length = int(text_min_length)
         self.sentence_min_length = int(sentence_min_length)
         self.min_ratio = float(min_ratio)
+        self.language_detector = annif.simplemma_util.get_language_detector(
+            self.project.language
+        )
 
     def transform_fn(self, text: str) -> str:
         if len(text) < self.text_min_length:
@@ -41,7 +43,7 @@ def transform_fn(self, text: str) -> str:
             if len(sent) < self.sentence_min_length:
                 retained_sentences.append(sent)
                 continue
-            proportion = in_target_language(sent, lang=(self.project.language,))
+            proportion = self.language_detector.proportion_in_target_languages(sent)
             if proportion >= self.min_ratio:
                 retained_sentences.append(sent)
         return " ".join(retained_sentences)
diff --git a/pyproject.toml b/pyproject.toml
index 970fd2503..487bb8649 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -45,7 +45,7 @@ numpy = "1.26.*"
 optuna = "3.6.*"
 python-dateutil = "2.9.*"
 tomli = { version = "2.0.*", python = "<3.11" }
-simplemma = "0.9.*"
+simplemma = "~1.1.1"
 jsonschema = "4.21.*"
 huggingface-hub = "0.22.*"
 
diff --git a/tests/test_simplemma_util.py b/tests/test_simplemma_util.py
new file mode 100644
index 000000000..57ea8b83e
--- /dev/null
+++ b/tests/test_simplemma_util.py
@@ -0,0 +1,19 @@
+"""Unit tests for Simplemma utility functions"""
+
+import pytest
+
+from annif.simplemma_util import get_language_detector
+
+
+def test_get_language_detector():
+    detector = get_language_detector("en")
+    text = "She said 'au revoir' and left"
+    proportion = detector.proportion_in_target_languages(text)
+    assert proportion == pytest.approx(0.75)
+
+
+def test_get_language_detector_many():
+    detector = get_language_detector(("en", "fr"))
+    text = "She said 'au revoir' and left"
+    proportion = detector.proportion_in_target_languages(text)
+    assert proportion == pytest.approx(1.0)