diff --git a/crypto/fipsmodule/rand/entropy/tree_drbg_jitter_entropy.c b/crypto/fipsmodule/rand/entropy/tree_drbg_jitter_entropy.c
index e388624192..db0e5f27cd 100644
--- a/crypto/fipsmodule/rand/entropy/tree_drbg_jitter_entropy.c
+++ b/crypto/fipsmodule/rand/entropy/tree_drbg_jitter_entropy.c
@@ -74,6 +74,8 @@ struct tree_jitter_drbg_t {
 
   // reseed_calls_since_initialization is the number of seed/reseed calls made
   // on |drbg| since its initialization.
+  // We assume 2^64-1 is an upper limit on number of reseeds. Type must support
+  // that.
   uint64_t reseed_calls_since_initialization;
 
   // generation_number caches the UBE generation number.
diff --git a/crypto/fipsmodule/rand/internal.h b/crypto/fipsmodule/rand/internal.h
index ff0f68c0e6..7ce0fc0750 100644
--- a/crypto/fipsmodule/rand/internal.h
+++ b/crypto/fipsmodule/rand/internal.h
@@ -45,6 +45,7 @@ struct ctr_drbg_state_st {
   uint8_t counter[16];
   uint64_t reseed_counter;
 };
+OPENSSL_STATIC_ASSERT((sizeof((struct ctr_drbg_state_st*)0)->reseed_counter) * 8 >= 48, value_can_overflow)
 
 // CTR_DRBG_init initialises |*drbg| given |CTR_DRBG_ENTROPY_LEN| bytes of
 // entropy in |entropy| and, optionally, a personalization string up to
diff --git a/crypto/fipsmodule/rand/rand.c b/crypto/fipsmodule/rand/rand.c
index 6cfeff2797..c63617dbbd 100644
--- a/crypto/fipsmodule/rand/rand.c
+++ b/crypto/fipsmodule/rand/rand.c
@@ -23,6 +23,8 @@ struct rand_thread_local_state {
 
   // reseed_calls_since_initialization is the number of reseed calls made on
   // |drbg| since its initialization.
+  // We assume 2^64-1 is an upper limit on number of reseeds. Type must support
+  // that.
   uint64_t reseed_calls_since_initialization;
 
   // generation_number caches the UBE generation number.
@@ -39,6 +41,7 @@ struct rand_thread_local_state {
   // process exit.
   CRYPTO_MUTEX state_clear_lock;
 };
+OPENSSL_STATIC_ASSERT((sizeof((struct rand_thread_local_state*)0)->generate_calls_since_seed) * 8 >= 48, value_can_overflow)
 
 DEFINE_BSS_GET(struct rand_thread_local_state *, thread_states_list_head)
 DEFINE_STATIC_MUTEX(thread_local_states_list_lock)