diff --git a/slsDetectorSoftware/include/sls/Pattern.h b/slsDetectorSoftware/include/sls/Pattern.h
index 64f1de29b..d43f4180d 100644
--- a/slsDetectorSoftware/include/sls/Pattern.h
+++ b/slsDetectorSoftware/include/sls/Pattern.h
@@ -30,7 +30,7 @@ class Pattern {
     bool operator!=(const Pattern &other) const;
     patternParameters *data();
     patternParameters *data() const;
-    constexpr size_t size() const noexcept { return sizeof(patternParameters); }
+    const size_t size() const noexcept { return sizeof(patternParameters); }
     void validate() const;
     void load(const std::string &fname);
     void save(const std::string &fname);
@@ -38,4 +38,4 @@ class Pattern {
 };
 
 } // namespace sls
-#endif
\ No newline at end of file
+#endif