diff --git a/src/json.hpp b/src/json.hpp
index e3caae435..6caa8defc 100644
--- a/src/json.hpp
+++ b/src/json.hpp
@@ -6191,7 +6191,7 @@ class basic_json
             }
 
             /// inequality operator (needed for range-based for)
-            constexpr bool operator!= (const iteration_proxy_internal& o) const
+            bool operator!= (const iteration_proxy_internal& o) const
             {
                 return anchor != o.anchor;
             }
diff --git a/src/json.hpp.re2c b/src/json.hpp.re2c
index 096c22cb9..7f311ef93 100644
--- a/src/json.hpp.re2c
+++ b/src/json.hpp.re2c
@@ -6191,7 +6191,7 @@ class basic_json
             }
 
             /// inequality operator (needed for range-based for)
-            constexpr bool operator!= (const iteration_proxy_internal& o) const
+            bool operator!= (const iteration_proxy_internal& o) const
             {
                 return anchor != o.anchor;
             }