diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6232a61f7..f689f5121 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -16,6 +16,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Deprecated
 - For the classes `Sink`, `Source` and `SourceAndSink`: `.sink`, `.source` and `.prevent_simultaneous_sink_and_source` are deprecated in favor of the new arguments `inputs`, `outputs` and `prevent_simultaneous_flow_rates`.
 
+### Fixed
+- Fixed testing issue with new `linopy` version 0.5.6 [[#296](https://github.com/PyPSA/linopy/pull/296) by [@FBumann](https://github.com/FBumann)]
+
 ## [2.1.5] - 2025-07-08
 
 ### Fixed
diff --git a/pyproject.toml b/pyproject.toml
index 8c846dc03..4624d3a00 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -38,7 +38,7 @@ dependencies = [
     "pandas >= 2.0.0, < 3",
 
     # Optimization and data handling
-    "linopy >= 0.5.1, < 0.6.0",
+    "linopy >= 0.5.1, < 0.5.6",  # Update and test regularly
     "netcdf4 >= 1.6.1, < 2",
 
     # Utilities
diff --git a/tests/conftest.py b/tests/conftest.py
index 5399be72a..c8d2e5606 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -450,22 +450,21 @@ def basic_flow_system_linopy(timesteps_linopy) -> fx.FlowSystem:
 
 def assert_conequal(actual: linopy.Constraint, desired: linopy.Constraint):
     """Assert that two constraints are equal with detailed error messages."""
-    name = actual.name
 
     try:
         linopy.testing.assert_linequal(actual.lhs, desired.lhs)
     except AssertionError as e:
-        raise AssertionError(f"{name} left-hand sides don't match:\n{e}") from e
+        raise AssertionError(f"{actual.name} left-hand sides don't match:\n{e}") from e
 
     try:
-        linopy.testing.assert_linequal(actual.rhs, desired.rhs)
+        xr.testing.assert_equal(actual.sign, desired.sign)
     except AssertionError as e:
-        raise AssertionError(f"{name} right-hand sides don't match:\n{e}") from e
+        raise AssertionError(f"{actual.name} signs don't match:\n{e}") from e
 
     try:
-        xr.testing.assert_equal(actual.sign, desired.sign)
+        xr.testing.assert_equal(actual.rhs, desired.rhs)
     except AssertionError as e:
-        raise AssertionError(f"{name} signs don't match:\nActual: {actual.sign}\nExpected: {desired.sign}") from e
+        raise AssertionError(f"{actual.name} right-hand sides don't match:\n{e}") from e
 
 
 def assert_var_equal(actual: linopy.Variable, desired: linopy.Variable):