diff --git a/CMakeLists.txt b/CMakeLists.txt
index 8c94083..3a6d588 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -35,12 +35,14 @@ FILE(GLOB TGC_VM_SOURCES ${CMAKE_CURRENT_SOURCE_DIR}/src/vm/interp/vm_*.cpp)
 set(LIB_SOURCES 
     src/vm/fp_functions.cpp
     src/plugin/instruction_count.cpp
-    src/plugin/cycle_estimate.cpp
     src/plugin/cov.cpp
     
     ${TGC_SOURCES}
     ${TGC_VM_SOURCES}
 )
+if(TARGET RapidJSON)
+    list(APPEND LIB_SOURCES src/plugin/cycle_estimate.cpp)
+endif()
 
 if(WITH_LLVM)
 	FILE(GLOB TGC_LLVM_SOURCES
@@ -82,6 +84,10 @@ elseif(TARGET elfio::elfio)
 else()
     message(FATAL_ERROR "No elfio library found, maybe a find_package() call is missing")
 endif()
+if(TARGET RapidJSON)
+    target_link_libraries(${PROJECT_NAME} PUBLIC RapidJSON)
+endif()
+
 
 set_target_properties(${PROJECT_NAME} PROPERTIES
   VERSION ${PROJECT_VERSION}
diff --git a/incl/iss/plugin/cycle_estimate.h b/incl/iss/plugin/cycle_estimate.h
index c2c9666..3f35dc7 100644
--- a/incl/iss/plugin/cycle_estimate.h
+++ b/incl/iss/plugin/cycle_estimate.h
@@ -39,6 +39,7 @@
 #include "iss/vm_plugin.h"
 #include <string>
 #include <unordered_map>
+#include <vector>
 
 namespace iss {
 
diff --git a/src/plugin/cycle_estimate.cpp b/src/plugin/cycle_estimate.cpp
index bf642f1..d2bcdad 100644
--- a/src/plugin/cycle_estimate.cpp
+++ b/src/plugin/cycle_estimate.cpp
@@ -41,6 +41,7 @@
 #include "rapidjson/writer.h"
 #include "rapidjson/stringbuffer.h"
 #include <rapidjson/ostreamwrapper.h>
+#include <rapidjson/error/en.h>
 #include <fstream>
 
 using namespace rapidjson;
@@ -67,13 +68,13 @@ bool iss::plugin::cycle_estimate::registration(const char* const version, vm_if&
                 Document d;
                 ParseResult ok = d.ParseStream(isw);
                 if(ok) {
-                    Value& val = d[core_name];
+                    Value& val = d[core_name.c_str()];
                     if(val.IsArray()){
                         delays.reserve(val.Size());
-                        for(auto it:val.GetArray()){
-                            auto name = it["name"];
-                            auto size = it["size"];
-                            auto delay = it["delay"];
+                        for (auto it = val.Begin(); it != val.End(); ++it) {
+                            auto& name = (*it)["name"];
+                            auto& size = (*it)["size"];
+                            auto& delay = (*it)["delay"];
                             if(delay.IsArray()) {
                                 delays.push_back(instr_desc{size.Get<unsigned>(), delay[0].Get<unsigned>(), delay[1].Get<unsigned>()});
                             } else if(delay.Is<unsigned>()) {
@@ -86,7 +87,7 @@ bool iss::plugin::cycle_estimate::registration(const char* const version, vm_if&
                         return false;
                    }
                 } else {
-                    LOG(ERR)<<"plugin cycle_estimate: could not parse in JSON file"<<endl;
+                    LOG(ERR)<<"plugin cycle_estimate: could not parse in JSON file at "<< ok.Offset()<<": "<<GetParseError_En(ok.Code())<<endl;
                     return false;
                }
             } catch (runtime_error &e) {