diff --git a/src/main/java/com/powsybl/openloadflow/sensi/AcSensitivityAnalysis.java b/src/main/java/com/powsybl/openloadflow/sensi/AcSensitivityAnalysis.java
index e49d1d1a48..d20e57b34a 100644
--- a/src/main/java/com/powsybl/openloadflow/sensi/AcSensitivityAnalysis.java
+++ b/src/main/java/com/powsybl/openloadflow/sensi/AcSensitivityAnalysis.java
@@ -79,12 +79,12 @@ private void calculateSensitivityValues(List<LfSensitivityFactor<AcVariableType,
                             ((SingleVariableLfSensitivityFactor<AcVariableType, AcEquationType>) factor).getVariableElement().equals(factor.getFunctionElement())) {
                         // add nabla_p eta, fr specific cases
                         // the only case currently: if we are computing the sensitivity of a phasetap change on itself
-                        Variable<AcVariableType> phi1Var = factor.getFunctionEquationTerm().getVariables()
+                        Variable<AcVariableType> a1Var = factor.getFunctionEquationTerm().getVariables()
                                 .stream()
-                                .filter(var -> var.getElementNum() == factor.getFunctionElement().getNum() && var.getType().equals(AcVariableType.BRANCH_ALPHA1))
+                                .filter(v -> v.getElementNum() == factor.getFunctionElement().getNum() && v.getType() == AcVariableType.BRANCH_ALPHA1)
                                 .findAny()
                                 .orElseThrow(() -> new PowsyblException("No alpha_1 variable on the function branch"));
-                        sensi += Math.toRadians(factor.getFunctionEquationTerm().der(phi1Var));
+                        sensi += Math.toRadians(factor.getFunctionEquationTerm().der(a1Var));
                     }
                 }
                 if (factor.getFunctionPredefinedResult() != null) {