diff --git a/src/lsa.cpp b/src/lsa.cpp
index 84bd5fe..5146dcd 100644
--- a/src/lsa.cpp
+++ b/src/lsa.cpp
@@ -138,7 +138,7 @@
 }
 
 bool
-CoordinateLsa::isEqualContent(const CoordinateLsa& clsa)
+CoordinateLsa::isEqualContent(const CoordinateLsa& clsa) const
 {
   if (clsa.getCorTheta().size() != m_angles.size()) {
     return false;
@@ -213,7 +213,7 @@
 }
 
 bool
-AdjLsa::isEqualContent(AdjLsa& alsa)
+AdjLsa::isEqualContent(const AdjLsa& alsa) const
 {
   return m_adl == alsa.getAdl();
 }
diff --git a/src/lsa.hpp b/src/lsa.hpp
index 7272aed..3d453d2 100644
--- a/src/lsa.hpp
+++ b/src/lsa.hpp
@@ -284,7 +284,7 @@
   }
 
   bool
-  isEqualContent(AdjLsa& alsa);
+  isEqualContent(const AdjLsa& alsa) const;
 
   /*! \brief Installs this LSA's name prefixes into the NPT.
 
@@ -384,7 +384,7 @@
   }
 
   bool
-  isEqualContent(const CoordinateLsa& clsa);
+  isEqualContent(const CoordinateLsa& clsa) const;
 
   void
   writeLog() const override;