diff --git a/environment.yml b/environment.yml
index 8b66a0113..3808235fe 100644
--- a/environment.yml
+++ b/environment.yml
@@ -23,7 +23,7 @@ dependencies:
 - hda>=2.22
 - pip:
   - multiurl>=0.3.3
-  - pyfdb>=0.1.0
+  - pyfdb>=0.1.0,<1.0
   - ecmwf-opendata>=0.1.2
   - polytope-client>=0.7.4
   - covjsonkit>=0.2.2
diff --git a/pyproject.toml b/pyproject.toml
index e0624f52b..2efd550c6 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -65,11 +65,11 @@ optional-dependencies.docs = [
   "sphinx-tabs"
 ]
 optional-dependencies.ecmwf-opendata = ["ecmwf-opendata>=0.3.3"]
-optional-dependencies.fdb = ["pyfdb>=0.1"]
+optional-dependencies.fdb = ["pyfdb>=0.1,<1.0"]
 optional-dependencies.geo = ["earthkit-geo>=0.2"]
 optional-dependencies.geopandas = ["geopandas"]
 optional-dependencies.geotiff = ["pyproj", "rasterio", "rioxarray"]
-optional-dependencies.gribjump = ["pyfdb>=0.1", "pygribjump"]
+optional-dependencies.gribjump = ["pyfdb>=0.1,<1.0", "pygribjump"]
 optional-dependencies.iris = ["ncdata>=0.3.2", "scitools-iris"]
 optional-dependencies.mars = ["ecmwf-api-client>=1.6.1"]
 optional-dependencies.odb = ["pyodc"]
diff --git a/tests/environment-unit-tests.yml b/tests/environment-unit-tests.yml
index 0297b177a..6995173ed 100644
--- a/tests/environment-unit-tests.yml
+++ b/tests/environment-unit-tests.yml
@@ -25,7 +25,7 @@ dependencies:
 - jsonschema
 - pip:
   - multiurl>=0.3.3
-  - pyfdb>=0.1.0
+  - pyfdb>=0.1.0,<1.0
   - ecmwf-opendata>=0.3.3
   - polytope-client>=0.7.4
   - git+https://github.com/ecmwf/earthkit-data-demo-source