diff --git a/IDEAS/Buildings/Components/Shading/HorizontalFins.mo b/IDEAS/Buildings/Components/Shading/HorizontalFins.mo
index 390a17986..245dbe54e 100644
--- a/IDEAS/Buildings/Components/Shading/HorizontalFins.mo
+++ b/IDEAS/Buildings/Components/Shading/HorizontalFins.mo
@@ -56,6 +56,7 @@ initial equation
 equation
   if not use_betaInput then
     beta_internal = beta;
+    Ctrl_to_beta_internal = 0;
   else
     beta_internal = Ctrl_to_beta_internal*beta_max;
     connect(Ctrl_to_beta_internal,Ctrl);
@@ -144,6 +145,10 @@ The implementation is illustrated using this figure:
 </html>", revisions="<html>
 <ul>
 <li>
+Febrauri 24, 2025 by Filip Jorissen:<br/>
+Added <code>Ctrl_to_beta_internal=0</code> when not using beta input. Otherwise the variable is undefined, resulting in a singular system.
+</li>
+<li>
 July 1, 2024 by Lucas Verleyen:<br/>
 Added <code>Ctrl_to_beta_internal</code> to linearly map the Ctrl input [0,1]
 onto the fin inclination angle [<code>0,beta_max</code>].<br/>
