diff --git a/share/libc/__fc_define_pthread_types.h b/share/libc/__fc_define_pthread_types.h
index d7be74b4d9d4bcfc5565d055002f92d70c256207..3e102d19894f21c048e0528be8cefd54c2c77254 100644
--- a/share/libc/__fc_define_pthread_types.h
+++ b/share/libc/__fc_define_pthread_types.h
@@ -50,7 +50,7 @@ typedef struct __fc_pthread_spinlock_t { int _fc; } pthread_spinlock_t;
 // such code to be parsed.
 typedef unsigned long pthread_t;
 #else
-typedef struct __fc_pthread_t { int _fc; } pthread_t;
+typedef struct __fc_pthread_t { unsigned long _fc; } pthread_t;
 #endif
 __END_DECLS
 __POP_FC_STDLIB
diff --git a/src/plugins/e-acsl/tests/concurrency/oracle/gen_parallel_threads.c b/src/plugins/e-acsl/tests/concurrency/oracle/gen_parallel_threads.c
index 7f656ff4aa67659c61002e0037cce0e3ea882059..c63e0856f119234bebfbb573d4b3d6f70b838f9e 100644
--- a/src/plugins/e-acsl/tests/concurrency/oracle/gen_parallel_threads.c
+++ b/src/plugins/e-acsl/tests/concurrency/oracle/gen_parallel_threads.c
@@ -1103,7 +1103,7 @@ int __gen_e_acsl_pthread_join(pthread_t thread, void **retval)
     int __gen_e_acsl_or;
     int __gen_e_acsl_valid_2;
     __e_acsl_store_block((void *)(& retval),8UL);
-    __e_acsl_store_block((void *)(& thread),4UL);
+    __e_acsl_store_block((void *)(& thread),8UL);
     __gen_e_acsl_contract = __e_acsl_contract_init(2UL);
     __e_acsl_assert_data_t __gen_e_acsl_assert_data = {.values = (void *)0};
     __e_acsl_assert_register_ptr(& __gen_e_acsl_assert_data,"retval",
@@ -1851,8 +1851,8 @@ int main(void)
   __e_acsl_store_block((void *)(& tmp_0),4UL);
   __e_acsl_store_block((void *)(& tmp),4UL);
   __e_acsl_store_block((void *)(args),40UL);
-  __e_acsl_store_block((void *)(readers),40UL);
-  __e_acsl_store_block((void *)(writers),40UL);
+  __e_acsl_store_block((void *)(readers),80UL);
+  __e_acsl_store_block((void *)(writers),80UL);
   __e_acsl_store_block((void *)(& __retres),4UL);
   __e_acsl_full_init((void *)(& tmp));
   tmp = __gen_e_acsl_pthread_mutex_init(& write_mutex,
diff --git a/src/plugins/e-acsl/tests/concurrency/oracle/gen_sequential_threads.c b/src/plugins/e-acsl/tests/concurrency/oracle/gen_sequential_threads.c
index ba28a676db6b9fb7449708c4eafb135d1741f684..08aa527836da75ff1801f7b3a1dec938dc19ad52 100644
--- a/src/plugins/e-acsl/tests/concurrency/oracle/gen_sequential_threads.c
+++ b/src/plugins/e-acsl/tests/concurrency/oracle/gen_sequential_threads.c
@@ -207,7 +207,7 @@ int __gen_e_acsl_pthread_join(pthread_t thread, void **retval)
     int __gen_e_acsl_or;
     int __gen_e_acsl_valid_2;
     __e_acsl_store_block((void *)(& retval),8UL);
-    __e_acsl_store_block((void *)(& thread),4UL);
+    __e_acsl_store_block((void *)(& thread),8UL);
     __gen_e_acsl_contract = __e_acsl_contract_init(2UL);
     __e_acsl_assert_data_t __gen_e_acsl_assert_data = {.values = (void *)0};
     __e_acsl_assert_register_ptr(& __gen_e_acsl_assert_data,"retval",
@@ -515,7 +515,7 @@ int main(void)
   __e_acsl_memory_init((int *)0,(char ***)0,8UL);
   __e_acsl_globals_init();
   __e_acsl_store_block((void *)(args),40UL);
-  __e_acsl_store_block((void *)(& t),4UL);
+  __e_acsl_store_block((void *)(& t),8UL);
   __e_acsl_store_block((void *)(& __retres),4UL);
   {
     int i = 0;
diff --git a/src/plugins/e-acsl/tests/concurrency/oracle/gen_threads_debug.c b/src/plugins/e-acsl/tests/concurrency/oracle/gen_threads_debug.c
index 6a4c17bd9fe799e43e81072c64d4c02488159519..329f8afa81c9d07634f0b0efe4550a700cacb64d 100644
--- a/src/plugins/e-acsl/tests/concurrency/oracle/gen_threads_debug.c
+++ b/src/plugins/e-acsl/tests/concurrency/oracle/gen_threads_debug.c
@@ -785,7 +785,7 @@ int __gen_e_acsl_pthread_join(pthread_t thread, void **retval)
     int __gen_e_acsl_or;
     int __gen_e_acsl_valid_2;
     __e_acsl_store_block((void *)(& retval),8UL);
-    __e_acsl_store_block((void *)(& thread),4UL);
+    __e_acsl_store_block((void *)(& thread),8UL);
     __gen_e_acsl_contract = __e_acsl_contract_init(2UL);
     __e_acsl_assert_data_t __gen_e_acsl_assert_data = {.values = (void *)0};
     __e_acsl_assert_register_ptr(& __gen_e_acsl_assert_data,"retval",
@@ -1533,8 +1533,8 @@ int main(void)
   __e_acsl_store_block((void *)(& tmp_0),4UL);
   __e_acsl_store_block((void *)(& tmp),4UL);
   __e_acsl_store_block((void *)(args),40UL);
-  __e_acsl_store_block((void *)(readers),40UL);
-  __e_acsl_store_block((void *)(writers),40UL);
+  __e_acsl_store_block((void *)(readers),80UL);
+  __e_acsl_store_block((void *)(writers),80UL);
   __e_acsl_store_block((void *)(& __retres),4UL);
   __e_acsl_full_init((void *)(& tmp));
   tmp = __gen_e_acsl_pthread_mutex_init(& write_mutex,
diff --git a/src/plugins/e-acsl/tests/concurrency/oracle/gen_threads_safe_locations.c b/src/plugins/e-acsl/tests/concurrency/oracle/gen_threads_safe_locations.c
index 3113cefa8b2f90ffb5b527648584b9295619fe39..2bb83096a37b444aaa320e4fa64a095c8e1e3c56 100644
--- a/src/plugins/e-acsl/tests/concurrency/oracle/gen_threads_safe_locations.c
+++ b/src/plugins/e-acsl/tests/concurrency/oracle/gen_threads_safe_locations.c
@@ -256,7 +256,7 @@ int __gen_e_acsl_pthread_join(pthread_t thread, void **retval)
     int __gen_e_acsl_or;
     int __gen_e_acsl_valid_2;
     __e_acsl_store_block((void *)(& retval),8UL);
-    __e_acsl_store_block((void *)(& thread),4UL);
+    __e_acsl_store_block((void *)(& thread),8UL);
     __gen_e_acsl_contract = __e_acsl_contract_init(2UL);
     __e_acsl_assert_data_t __gen_e_acsl_assert_data = {.values = (void *)0};
     __e_acsl_assert_register_ptr(& __gen_e_acsl_assert_data,"retval",
@@ -562,7 +562,7 @@ int main(void)
   pthread_t t;
   __e_acsl_memory_init((int *)0,(char ***)0,8UL);
   __e_acsl_globals_init();
-  __e_acsl_store_block((void *)(& t),4UL);
+  __e_acsl_store_block((void *)(& t),8UL);
   __e_acsl_store_block((void *)(& __retres),4UL);
   __gen_e_acsl_pthread_create(& t,(pthread_attr_t const *)0,& thread_start,
                               (void *)0);
diff --git a/tests/libc/oracle/fc_libc.1.res.oracle b/tests/libc/oracle/fc_libc.1.res.oracle
index 8bc8f679bba9a04c85d13e4e3d60bde10a6fa53b..b5874f1ef25baa4b60527857038a1a5052e3bc20 100644
--- a/tests/libc/oracle/fc_libc.1.res.oracle
+++ b/tests/libc/oracle/fc_libc.1.res.oracle
@@ -113,7 +113,7 @@ struct __fc_pthread_mutexattr_t {
 };
 typedef struct __fc_pthread_mutexattr_t pthread_mutexattr_t;
 struct __fc_pthread_t {
-   int _fc ;
+   unsigned long _fc ;
 };
 typedef struct __fc_pthread_t pthread_t;
 typedef int pid_t;