diff --git a/src/iso19111/c_api.cpp b/src/iso19111/c_api.cpp
index 7c835c15ab..2f408cb2c1 100644
--- a/src/iso19111/c_api.cpp
+++ b/src/iso19111/c_api.cpp
@@ -521,10 +521,13 @@ PJ *proj_clone(PJ_CONTEXT *ctx, const PJ *obj) {
             if (newPj) {
                 newPj->descr = "Set of coordinate operations";
                 newPj->ctx = ctx;
+                const int old_debug_level = ctx->debug_level;
+                ctx->debug_level = PJ_LOG_NONE;
                 for (const auto &altOp : obj->alternativeCoordinateOperations) {
                     newPj->alternativeCoordinateOperations.emplace_back(
                         PJCoordOperation(ctx, altOp));
                 }
+                ctx->debug_level = old_debug_level;
             }
             return newPj;
         }