diff --git a/fido2/device.h b/fido2/device.h
index ea46123..4692323 100644
--- a/fido2/device.h
+++ b/fido2/device.h
@@ -61,8 +61,8 @@ int ctap_user_presence_test(uint32_t delay);
 int ctap_generate_rng(uint8_t * dst, size_t num);
 
 // Increment atomic counter and return it.
-// Must support two counters, @sel selects counter0 or counter1.
-uint32_t ctap_atomic_count(int sel);
+// @param amount the amount to increase the counter by.
+uint32_t ctap_atomic_count(uint32_t amount);
 
 // Verify the user
 // return 1 if user is verified, 0 if not
diff --git a/pc/device.c b/pc/device.c
index ee6bae7..791f8c9 100644
--- a/pc/device.c
+++ b/pc/device.c
@@ -313,20 +313,11 @@ int ctap_user_verification(uint8_t arg)
 }
 
 
-uint32_t ctap_atomic_count(int sel)
+uint32_t ctap_atomic_count(uint32_t amount)
 {
     static uint32_t counter1 = 25;
-    /*return 713;*/
-    if (sel == 0)
-    {
-        printf1(TAG_RED,"counter1: %d\n", counter1);
-        return counter1++;
-    }
-    else
-    {
-        printf2(TAG_ERR,"counter2 not imple\n");
-        exit(1);
-    }
+    counter1 += amount;
+    return counter1;
 }
 
 int ctap_generate_rng(uint8_t * dst, size_t num)
diff --git a/targets/stm32l432/src/device.c b/targets/stm32l432/src/device.c
index 532c407..2a23cbe 100644
--- a/targets/stm32l432/src/device.c
+++ b/targets/stm32l432/src/device.c
@@ -407,7 +407,7 @@ void authenticator_write_state(AuthenticatorState * a, int backup)
     }
 }
 
-uint32_t ctap_atomic_count(int sel)
+uint32_t ctap_atomic_count(uint32_t amount)
 {
     int offset = 0;
     uint32_t * ptr = (uint32_t *)flash_addr(COUNTER1_PAGE);
@@ -422,10 +422,12 @@ uint32_t ctap_atomic_count(int sel)
 
     uint32_t lastc = 0;
 
-    if (sel != 0)
+    if (amount == 0)
     {
-        printf2(TAG_ERR,"counter2 not imple\n");
-        exit(1);
+        // Use a random count [1-16].
+        uint8_t rng[1];
+        ctap_generate_rng(rng, 1);
+        amount = (rng[1] & 0x0f) + 1;
     }
 
     for (offset = 0; offset < PAGE_SIZE/4; offset += 2) // wear-level the flash
@@ -458,7 +460,7 @@ uint32_t ctap_atomic_count(int sel)
         return lastc;
     }
 
-    lastc++;
+    lastc += amount;
 
     if (lastc/256 > erases)
     {